Polymer precursor, high transparency polyimide precursor, polymer compound, resin composition and article using thereof

ABSTRACT

A polymer precursor including a part which sequences an unsaturated bond having a π electron orbit and a single bond alternately is disclosed. The polymer precursor has a first functional group and a second functional group which form a repeating unit constituting a polymer skeleton of an end product by an intramolecular reaction. At least a part of a conjugated state formed by the π electron orbit in the molecule is disconnected or weakened due to a three-dimensional structure of the molecule and a transmittance with respect to an electromagnetic wave of at least one wavelength selected from the group consisting of 436 nm, 405 nm, 365 nm, 248 nm and 193 nm is improved.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polymer precursor excellent intransparency with respect town electromagnetic wave in an ultravioletrange. Particularly, the present invention relates to a polymerprecursor, a polymer compound derived from the polymer precursor and aresin composition containing the polymer precursor which can be suitablyutilized as material of a product or member formed through a patterningprocess by an electromagnetic wave, for instance, a forming material ofoptical goods or optical parts, an insulating material, a layer formingmaterial or an adhesive or the like, and an article produced with theuse of the polymer precursor, the polymer compound or the resincomposition.

Suitably, the present invention relates to a polyimide precursorexcellent in transparency with respect to an electromagnetic wave in anultraviolet range. Particularly, the present invention relates to hightransparency polyimide precursor which can be suitably utilized asmaterial of a product or member formed through a patterning process byan electromagnetic wave, for instance, a forming material of opticalgoods or optical parts, an insulating material, a layer forming materialor an adhesive or the like and is excellent in heat resistance andtransparency after imidization. Further, the present invention relatesto high transparency polyimide derived from the high transparencypolyimide precursor, a resin composition containing the hightransparency polyimide precursor and an article produced with the use ofthe high transparency polyimide precursor, the high transparencypolyimide or the resin composition.

2. Description of the Related Art

Polymer material is used for various familiar products due to itsproperties such as high processability, lightness in weight or the like.Polyimide developed by DuPont, U.S., in 1955 has been further developedso as to apply to an aerospace field or the like because of itsexcellent heat resistance. Since then, in detailed studies done by manyresearchers, it was found that properties such as heat resistance,dimensional stability, insulating property and the like are good amongorganic matters showing top-class properties, hence, polyimide has beenapplied not only to the aerospace field but also to an insulatingmaterial of electronic parts and the like. Nowadays, polyimide isincreasingly utilized as a chip coating layer of a semiconductorelement, a substrate of a flexible printed-wiring board and the like.

Also, in recent years, in order to solve problems of the polyimide,compounds having a similar engineering process as the imidazole such aspolybenzoxazole having low water absorption rate and low permittivity,polybenzimidazole excellent in adhesion property to a substrate and thelike are vigorously researched.

Polyimide is a polymer which is synthesized from diamine and aciddianhydride. Precursor of polyimide (polyamic acid) is obtained byreacting diamine and acid dianhydride in liquid. Then, polyimide can beobtained through a dehydration and ring-closure reaction. Generally,since polyimide is poor in solubility to a solvent and difficult toprocess, polyimide is often obtained by making its precursor, which ispolyamic acid, into a desired form followed by heating. Polyamic acidoften decomposes by heat or water, thus, it is not good in storagestability. Taking the point into consideration, polyimide, which isimproved in such a manner that a skeleton excellent in solubility isintroduced to a molecular structure to obtain polyimide so as to be ableto dissolve the polyimide into a solvent to form or apply, has beendeveloped. However, this polyimide tends to be inferior in chemicalresistance or adhesion to a substrate to the polyimide obtained by themeans using a precursor. Hence, either means using a precursor or meansusing solvent-soluble polyimide is used in accordance with the purpose.

Also, with the advancement of technology, there has been demand forpatterning polyimide in a desired form. Hence, polyimide which iscapable of pattern forming through processes such as exposure,development and so on using an electromagnetic wave such as ultravioletray or the like has been developed. Several means are proposed forpatterning polyimide. One of them is a method to obtain a pattern ofpolyimide in such a manner that patterning is performed in a state ofpolyimide precursor followed by imidization with thermal treatment orthe like. Another method is to obtain a pattern in such a manner that aresist pattern is formed on polyimide itself by organic matters, metalsor the like, opening of the resist pattern is treated with a solventsuch as hydrazine, inorganic alkali, organic alkali or the like, anorganic polar solvent or a mixture thereof to decompose or elute.

The former has an advantage that it is excellent in processability byusing a precursor excellent in a solvent solubility. The latter has anadvantage that an imidization process which requires a thermal treatmentat high temperature or the like is not necessary after pattern forming.The former and the latter are used in accordance with required usethereof.

In the area of semiconductor which has been achieved remarkabledevelopment from the last half of the 20^(th) century, presently,polyimide of a type utilizing a precursor capable of patterning ismainly used since, as one reason, polyimide is formed on a silicon wafersubstrate, the substrate can tolerate a thermal treatment of hightemperature at 300° C. to 400° C. required for imidization.

As means for polyimide patterning of a type utilizing a precursor,various means are proposed. Representative means thereof can beclassified broadly into the following two categories :

(1) a means in which a photosensitive resin layer is formed on a surfaceof a polyimide precursor and the polyimide precursor is patterned by apattern of the photosensitive resin as the polyimide precursor itselfdoes not have patterning ability; and

(2) a means of pattern forming by an effect of introducing aphotosensitive portion to a polyimide precursor itself by bonding orcoordinating, a means of pattern forming by an effect of aphotosensitive component in a resin composition which is a polyimideprecursor mixed with the photosensitive component, and further, a meansof a combination of introducing the photosensitive portion and mixingthe photosensitive component.

As a representative means of the above (1) group, there is a means ofobtaining a polyimide pattern in such a manner that utilizing solubilityof polyamic acid, which is a polyimide precursor, to an alkali solvent,on a coating layer of the polyamic acid in the alkali solvent, a resistcapable of an alkali development is applied followed by irradiation withan electromagnetic wave in a desired form; simultaneously as developmentof the resist, polyamic acid exposed from opening of the resist appearedby the development is also eluted in a developer to form a pattern; andthen a resist layer on a surface is peeled by an organic solvent towhich the polyamic acid is insoluble such as acetone or the likefollowed by imidization.

On the other hand, as a representative means of the above (2) group, thefollowing means are proposed:

(a) a means of obtaining a polyimide pattern in such a manner thatpattern forming is performed by mixing polyamic acid, which is aprecurso2r of polyimide, with a naphthoquinonediazide derivative, whichfunctions as a dissolution inhibitor before exposure of anelectromagnetic wave and as a dissolution promoter after exposure toproduce carboxylic acids, so as to enlarge contrast of dissolution rateof an exposed part and that of an unexposed part with respect to adeveloper; and imidization is performed;

(b) a means of obtaining a polyimide pattern in such a manner thatpattern forming is performed by mixing polyamic acid, which is aprecursor of polyimide, with a compound which is a basic substanceexhibiting catalytic activity of imidization by exposure of anelectromagnetic wave such as a nifedipine derivative or the likefollowed by heating at an appropriate temperature after exposure so thatan exposed part is subject to partial imidization due to the effect ofthe basic substance produced on the exposed part, and thereby loweringsolubility of the exposed part with respect to a developer so as toenlarge contrast of dissolution rate of the exposed part and that of anunexposed part with respect to the developer; and imidization isperformed completely;

(c) a means of obtaining a polyimide pattern in such a manner thatpattern forming is performed by mixing a polyimide precursor having askeleton having a radically polymerizable ethylenically unsaturated bondwith a photoradical initiator so as to form a cross-linked structure onan exposed part to lower solubility with respect to a developer, andthereby enlarging contrast of dissolution rate of the exposed part andthat of an unexposed part with respect to a developer; and imidizationis performed;

(d) a means of obtaining a polyimide pattern in such a manner thatpattern forming is performed by mixing polyamic acid as a polyimideprecursor with a skeleton having a basic part and an radicallypolymerizable ethylenically unsaturated bond to be bonded ionically;mixing a photoradical initiator thereto to form a cross-linked structureat an exposed part so as to lower solubility with respect to adeveloper, and thereby enlarging contrast of dissolution rate of theexposed part and that of an unexposed part with respect to thedeveloper; and imidization is performed; and

(e) a means of obtaining a polyimide pattern in such a manner thatpattern forming is performed by mixing polyamic acid as a precursor ofpolyimide with a photoacid (or photobase) generator and a crosslinkingagent followed by exposure and heating to proceed crosslinking by theeffect of acid (or base) generated by the exposure, and thereby loweringsolubility with respect to a developer so as to enlarge contrast ofdissolution rate of an exposed part and that of an unexposed part withrespect to the developer; and imidization is performed.

The above-mentioned means of (1) group is characterized in that, thoughthe process is more complicated, the degree of freedom of composition ofthe polyimide precursor to be used is high. Also, impurity other thanpolyimide is not contained in final polyimide since a photosensitivecomponent or the like is not mixed, hence, the above-mentioned means of(1) group is high in reliability.

On the other hand, the means of (2) group is characterized in that sincethe polyimide precursor (or the polyimide precursor resin composition)itself has pattern forming ability, the resist layer used in the (1)group is not necessary, hence, process is largely simpler. However, ifthe polyimide precursor itself does not fully transmit the exposurewavelength, problems may be raised such as decline in sensitivity, notcapable of forming a pattern and the like since the electromagnetic wavemay not reach the photosensitive component. Therefore, it is necessaryto select a skeleton high in transmittance with respect to the exposurewavelength.

In accordance with a demand of the market for forming a finer pattern,shorter exposure wavelength is used gradually shifting from 436 nm to405 nm or 365 nm. The polyimide precursor used for the above-mentionedmeans is different in absorption wavelength according to the chemicalstructure. Generally, the polyimide precursor often has absorption fromaround 450 nm to the short wavelength side. Particularly, the tendencyis strong in a polyimide precursor having many aromatic structures, apart of which or most part of which is in a conjugated state. Also, thepolyimide precursor in which efforts are made to make the absorptionsmaller often has absorption in the wavelength of 400 nm or less. Inorder to correspond to the exposure at the wavelength of 365 nm or lessbeing capable of a finer process, improvement of transmittance withrespect to shorter wavelength has been studied.

Particularly, a polyimide precursor having an aromatic skeletonexhibiting high heat resistance and low coefficient of expansion tendsto have absorption in longer wavelength range.

The reason of the absorption of the polyimide precursor is said to becharge transfer. Recently, it is reported that particularly chargetransfer in a molecule is highly related to coloring (Polymer Preprints,Japan 48 [5] 939 (1999)). That is, a polyimide precursor which hasabsorption in shorter wavelength range can be formed by eliminating thecharge transfer in the molecule. Based on this principle, asconventional means to shift absorption of the polyimide precursor toshorter wavelength, two major means are proposed.

One means is to shift absorption to shorter wavelength by introducing analiphatic structure, particularly an alicyclic structure, to a polyimideprecursor skeleton in which there are normally many aromatic skeletonsto disconnect conjugation of π electron in the skeleton so as to inhibitcharge transfer in the skeleton. Particularly, it is disclosed to beeffective to introduce an alicyclic skeleton to diamine which is astarting material (Polymer Preprints, Japan 48 [5] 939 (1999), andJapanese Patent Application Laid-Open (JP-A) No. Hei. 10-310639).

The other means is to provide transparency by introducing fluorine in apolyimide precursor skeleton so as to hinder charge transfer in anelectronic state of the skeleton (JP-A No. Hei. 05-1148).

As for a polyimide precursor using 2,2′,6,6-biphenyltetracarboxylicdianhydride as an acid component, Goin et al., U.S., discloses inPOLYMER LETTERS Vol. 6, p. 821-825 (1968) that after refining polyamicacid obtained by reacting 2,2′,6,6′-biphenyltetracarboxylic dianhydridewith 4,4′-diamino diphenyl ether in dimethylacetamide by reprecipitationusing diethyl ether, polyamic acid liquid obtained by being dissolvedagain in dimethylacetamide is cast followed by heating gradually up to300° C., and thus obtained polyimide. The thermally decomposingtemperature of polyimide is merely disclosed herein, and other physicalproperties are not stated in detail.

Also, JP-ANo. Sho. 56-52722 similarly discloses to utilize polyimidesynthesized by using 2,2′,6,6′-biphenyltetracarboxylic dianhydride and4,4-diamino diphenyl ether as a liquid crystal orientation layer,however, an ability to orient a liquid crystal is merely disclosedherein, and other physical properties are not disclosed.

In Example of JP-A No. Hei. 6-41205 polyimide using2,2′,6,6′-biphenyltetracarboxylic dianhydride is disclosed, however, thepolyimide is used as a protective layer which prevents polymers fromadhering to a polymerization container. It is mentioned about a primarycoloring of the polymer produced in the polymerization container havingthe protective layer provided, however, physical properties of polyimideprecursor are not stated at all.

JP-A No. Hei. 6-329799 discloses a method for producing a molded body ofpolyimide and 2,2′,6,6′-biphenyltetracarboxylic dianhydride is mentionedas one representative example of a starting material, however, compoundnames are merely listed without actual synthesis examples, thus, nospecific physical property can be learned.

JP-A No. Hei. 11-140181 discloses a method for producing polyimidemicroparticles and 2,2′,6,6′-biphenyltetracarboxylic dianhydride ismentioned herein as a representative example of a starting material,however, compound names are merely listed without actual synthesisexamples, thus, no specific physical property can be learned.

JP-A No. 2002-60489 discloses polyimide and an adhesive tape obtainedusing the same. 2,2′,6,6′-biphenyltetracarboxylic dianhydride is alsomentioned herein as a representative example of a starting material,however, compound names are merely listed without actual synthesisexamples, thus, no specific physical property can be learned.

JP-A No. Hei. 3-275725 discloses a method for producing aphotoconductive polymer. 2,2′,6,6′-biphenyltetracarboxylic dianhydrideis also mentioned herein as a representative example of a material,however, compound names are merely listed without actual synthesisexample, thus, no specific physical property can be learned.

SUMMARY OF THE INVENTION

All of the above-mentioned conventional means for improving transparencyof the polyimide precursor accordingly induce decrease in physicalproperties of polyimide to be finally obtained.

The first means has a problem that an alicyclic structure tends to bemore easily oxidized than an aromatic structure, thus colored byoxidization when heated in air. Hence, it is recommended to heatpolyimide having an alicyclic structure introduced under inertatmosphere. Also, the polyimide having an alicyclic structure introducedhas a lower thermally decomposing temperature than the aromaticpolyimide, thus, it is inferior in heat resistance. Further, in the caseof raising the coefficient of linear thermal expansion and forming aninterface with a substance having the small thermal expansioncoefficient such as metal, metal oxide, silicon wafer or the like, awarpage may be generated or deterioration in adherence may be caused dueto a heat history.

Also, in the case of using diamine having an alicyclic structure as astarting material, diamine having an alicyclic structure has higherbasicity than aromatic diamine, thus, when a polymerization reaction isperformed with acid dianhydride, a salt is formed with carboxylic acidof polyamic acid produced, thus, it becomes difficult to increase amolecule weight. Therefore, a silylation method (a method to sililate anamino group and then to polymerize with acid dianhydride) or the like isproposed, however, increase of one synthesis process causes increase incost.

On the other hand, the second means has a problem that by introducingfluorine to polyimide, cost of a material rises leading to increase incost. Also, introducing fluorine causes decrease in adhesion of aninterface, thus it becomes easy to be peeled from a substrate. Also,solvent resistance declines, and the glass transition temperature alsolowers. Further, as the coefficient of linear thermal expansion becomeslarger, a warpage of a substrate or decrease in adhesion may be causedwhen forming is performed on a substrate having a small thermalexpansion coefficient.

Also, conventionally, in polyamic acid, which is one kind of a polyimideprecursor, if tetracarboxylic dianhydride being used is aromatic series,two carbonyl groups finally forming an imide bond are bonded to the samearomatic ring in a π conjugated state, an amide bond and the carboxylicacid are close in the state of polyimide precursor after reaction withdiamine, and their binding positions with the aromatic ring is fixed.Since the reaction between acid anhydride and amine is a reversiblereaction, in such a state, a reverse reaction is more likely to occur.Hence, a reverse reaction proceeds due to a long-term storage andheating so that a molecular chain breaks to lower molecular weight, or areactive end generated by the reverse reaction reacts with various partsto cause gelation. Therefore, hypothermic or frozen storage isrecommended for the polyimide precursor represented by polyamic acid andhandling of the polyimide precursor has been a problem.

The present invention has been achieved in light of the above-statedconventional problems. An object of a polymer precursor of the presentinvention is to provide a polymer precursor which exhibits hightransmittance to a shorter wavelength range with respect to anelectromagnetic wave, though the polymer precursor has a part whichsequences an unsaturated bond having a π electron orbit and a singlebond alternately.

An object of a photosensitive resin composition of the present inventionis to provide a photosensitive resin composition which is high insensitivity and can be exposed by an electromagnetic wave of shorterwavelength using the polymer precursor having high transmittance to ashort wavelength range with respect to an electromagnetic wave and/orhaving excellent storage stability.

Another object of the present invention is to provide various kinds ofproducts or members made of a polymer compound derived from the polymerprecursor or containing the polymer compound using the polymer precursorhaving high transmittance to a short wavelength range with respect to anelectromagnetic wave and/or excellent storage stability.

An object of a polyimide precursor of the present invention is toprovide a polyimide precursor which has high transmittance in a shorterwavelength range with respect to an electromagnetic wave withoutdamaging original properties as polyimide such as heat resistance or thelike of polyimide to be finally obtained.

An object of a photosensitive resin composition of the present inventionis to provide a photosensitive resin composition which has highsensitivity and can be exposed by an electromagnetic wave of a shorterwavelength using the polyimide precursor having high transparency and/orexcellent storage stability.

Another object of the present invention is to provide various kinds ofproducts or members made of polyimide derived from the polyimideprecursor or containing the polyimide using the polyimide precursorhaving high transmittance in a short wavelength range with respect to anelectromagnetic wave and/or excellent storage stability.

The present invention solves at least one of the above objects.

A polymer precursor of the present invention to solve the aforementionedproblems comprises a polymer containing a part which sequences anunsaturated bond having a π electron orbit and a single bondalternately,

wherein the polymer precursor has a first functional group and a secondfunctional group which form a repeating unit constituting a polymerskeleton of an end product by an intramolecular reaction,

wherein at least a part of a conjugated state formed by the π electronorbit in the molecule is disconnected or weakened due to athree-dimensional structure of the molecule, and

wherein a transmittance with respect to an electromagnetic wave of atleast one wavelength selected from the group consisting of 436 nm, 405nm, 365 nm, 248 nm and 193 nm is larger than an expected transmittanceprovided that the conjugated state is under neither disconnectedcondition nor weakened condition.

The polymer containing a part which sequences an unsaturated bond havinga π electron orbit and a single bond alternately generally tends to havethe conjugated state formed by the n electron orbit in the molecule.However, in the polymer precursor of the present invention, theconjugated state, which will be generally formed, is disconnected orweakened due to the three-dimensional structure in the molecule, thus,stabilization of the π electron orbit is inhibited. As a result,absorption in a long wavelength range vanishes or becomes smaller,hence, the polymer precursor exhibits high transmittance in a shorterwavelength range with respect to an electromagnetic wave.

As a preferable embodiment of the polymer precursor of the presentinvention, a polymer precursor, wherein the part which sequences anunsaturated bond having a π electron orbit and a single bond alternatelyhas a first site and a second site which are different from each other,wherein the first functional group and the first site, and the secondfunctional group and the second site are respectively bonded directly orvia other atom, and wherein the conjugated state formed between thefirst site and the second site is disconnected or weakened due to thethree-dimensional structure of the molecule, is provided.

In the case that the first functional group and the second functionalgroup are present on the same part which sequences an unsaturated bondhaving a π electron orbit and a single bond alternately, the firstfunctional group and the second functional group are fixed in a certainclose positional relationship. Hence, storage stability may bedeteriorated such as breaking of polymer chain or causing gelation as aside reaction proceeds in a state without adjusting reaction condition,for instance, a long-term storage or by heating. To the contrary, in thecase that the conjugated state usually formed between the first sitehaving the first functional group bonded and the second site having thesecond functional group bonded in the molecule is disconnected orweakened by the three-dimensional structure of the molecule, the firstfunctional group and the second functional group becomethree-dimensionally apart. Thus, the side reaction of the firstfunctional group and the second functional group is inhibited fromproceeding upon storage. As a result, storage stability of the polymerprecursor improves. When it is necessary to derive the polymer precursorto the polymer compound, which is an end product, only an intramolecularreaction required originally can be proceeded by adjusting a reactioncondition.

As other preferable embodiment of the polymer precursor of the presentinvention, a polymer precursor, wherein the polymer precursor has aportion which exhibits effect that the polymer precursor itself is curedor solubility of the polymer precursor itself is changed by irradiationwith radiation having a wavelength of 440 nm or less in a molecule; orthe polymer precursor has a portion which exhibits effect that thepolymer precursor itself is cured or solubility of the polymer precursoritself is changed by effect of a compound having absorption in anelectromagnetic wave having a wavelength of 440 nm or less in amolecule, is provided.

In the case that the polymer precursor has a reactive portion asmentioned above in the molecule, patterning can be performed byradiations, particularly an electromagnetic wave in a short wavelengthrange.

Next, a polymer precursor resin composition of the present inventioncontains the polymer precursor of the present invention.

As a preferable embodiment of the polymer precursor resin composition ofthe present invention, a polymer precursor resin composition, whereinthe polymer precursor has a photosensitive portion which cures thepolymer precursor resin composition or changes solubility of the polymerprecursor resin composition when irradiated with an electromagnetic wavehaving a wavelength of 440 nm or less in a molecule; and/or the polymerprecursor resin composition further contains a photosensitive componenthaving the photosensitive portion, is provided.

In the case that the polymer precursor resin composition contains thepolymer precursor having the photosensitive portion and/or thephotosensitive component having the photosensitive portion, patterningcan be performed by radiations, particularly an electromagnetic wave ina short wavelength range.

Next, a polymer compound of the present invention is a polymer compoundwhich is obtained by reacting the polymer precursor of the presentinvention.

Further, a polymer compound resin composition of the present inventionis a polymer compound resin composition obtained by reacting the polymerprecursor resin composition of the present invention.

The polymer compound obtained from the polymer precursor as an endproduct and the polymer compound resin composition obtained from thepolymer precursor resin composition as an end product can be utilizedfor all fields and products in which a resin material is conventionallyused such as pattern forming materials (resists), coating materials,paints, printing inks, adhesives, fillers, electronic materials, moldingmaterials, resist materials, building materials, 3D modelings, flexibledisplay films, optical members or the like.

Since normally the conjugated state in the molecule is disconnected orweakened even as an end product as same as in the stage of theprecursor, the polymer compound and polymer compound resin compositionof the present invention have high transparency. Therefore, it isparticularly suitable for forming products of fields in whichtransparency is required, for example, paints, printing inks, colorfilters, flexible display films, electronic parts, layer insulationfilms, wire cover films, optical circuits, optical circuit parts,antireflection films, holograms, other optical members or buildingmaterials.

Also, a high transparency polyimide precursor of the present inventionis one of the preferable polymer precursors of the present invention andhas a repeating unit represented by the formula (1a) or (1b) or has bothrepeating units represented by the following formulae (1a) and (1b):

wherein, each of R¹ to R⁶ is independently a hydrogen atom or amonovalent organic group, which may be bonded each other; each of R⁷ andR⁸ is independently a hydrogen atom or a monovalent organic group; “X”is a divalent organic group; each of R⁹ and R¹⁰ is independently ahydrogen atom or a monovalent organic group; and groups represented bythe same symbol among repeating units in the same molecule may bedifferent atoms or structures.

A skeleton contained in the repeating unit represented by the formula(1a) or (1b) is unstable when arranged in a plane, thus, a relativeposition of a benzene ring of a biphenyl structure derived fromdianhydride contained in the skeleton twists and a conjugation of a πbond is disconnected.

Since the high transparency polyimide precursor of the present inventionhas such a spatial configuration of a molecular structure, a πconjugation on a polyimide precursor molecular chain is inhibited so asto obtain a polyimide precursor having absorption in shorter wavelength.Also, polyimide finally obtainable from the polyimide precursor has heatresistance as the polyimide is an aromatic polyimide. Also, thoughdepending on a structure, there is a wide range of selection ofstructure since the polyimide does not have absorption in 400 nm or morein combination with various diamines. As a result, without limit inabsorption wavelength, the skeleton can be selected according to therequired physical properties such as low thermal expansion or lowmoisture absorptivity, low permittivity or low dielectric tangent or thelike.

Also, a carbonyl group and an amide group finally forming an imide bondare not bonded to the same aromatic ring in a π conjugated structure,the carbonyl group and the amide group are three-dimensionally apart inthe state of polyimide precursor, the polyimide precursor of the presentinvention is superior in storage stability compared to the conventionalpolyamic acid or the like.

As other preferable embodiment of the high transparency polyimideprecursor of the present invention, a high transparency polyimideprecursor, wherein the high transparency polyimide precursor has aportion which exhibits effect that the high transparency polyimideprecursor itself is cured or solubility of the high transparencypolyimide precursor itself is changed by irradiation with anelectromagnetic wave having a wavelength of 440 nm or less in amolecule; or the high transparency polyimide precursor has a portionwhich exhibits effect that the high transparency polyimide precursoritself is cured or solubility of the high transparency polyimideprecursor itself is changed by effect of a compound having absorption inan electromagnetic wave having a wavelength of 440 nm or less in amolecule, is provided.

In the case that the high transparency polyimide precursor has areactive portion as mentioned above in the molecule, patterning can beperformed by radiations, particularly an electromagnetic wave in a shortwavelength range.

Next, a polyimide precursor resin composition of the present inventioncontains the high transparency polyimide precursor of the presentinvention.

As a preferable embodiment of the polyimide precursor resin compositionof the present invention, a polyimide precursor resin composition,wherein the high transparency polyimide precursor has a photosensitiveportion which cures the polyimide precursor resin composition or changessolubility of the polyimide precursor resin composition when irradiatedwith an electromagnetic wave having a wavelength of 440 nm or less in amolecule; and/or the polyimide precursor resin composition furthercontains a photosensitive component having the photosensitive portion,is provided. The high transparency polyimide precursor or thephotosensitive component may be contained solely in the polyimideprecursor resin composition or two or more kinds may be contained in thesame polyimide precursor resin composition.

In the case that the polyimide precursor resin composition contains thehigh transparency polyimide precursor having the photosensitive portionand/or the photosensitive component having the photosensitive portion,patterning can be performed by radiations, particularly anelectromagnetic wave in a short wavelength range, further anelectromagnetic wave having a wavelength of 400 nm or less.

Next, polyimide of the present invention is polyimide which is obtainedby reacting the high transparency polyimide precursor of the presentinvention.

Further, a polyimide resin composition of the present invention is apolyimide resin composition obtained by reacting the polyimide precursorresin composition of the present invention.

The polyimide obtained from the high transparency polyimide precursor asan end product and the high transparency polyimide obtained from thepolyimide precursor resin composition as an end product can be utilizedfor all fields and products in which a resin material is conventionallyused such as pattern forming materials (resists), coating materials,paints, printing inks, adhesives, fillers, electronic materials, moldingmaterials, resist materials, building materials, 3D modelings, flexibledisplay films, optical members or the like.

The polyimide and polyimide resin composition of the present inventionare mainly used as a pattern forming material (resist). A pattern formedthereby functions as a permanent film imparting heat resistance orinsulation. Also, since a conjugated state in a molecule is disconnectedor weakened even as an end product as same as in the stage of theprecursor, the polyimide and polyimide resin composition of the presentinvention have high transparency.

Therefore, it is particularly suitable for forming products of fields inwhich transparency is required as well as heat resistance or insulation,for example, paints, printing inks, color filters, flexible displayfilms, electronic parts, layer insulation films, wire cover films,optical circuits, optical circuit parts, antireflection films,holograms, other optical members or building materials.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings,

FIG. 1 is a spatial configuration presumed from the result of the MM2molecular orbital calculation of a model compound having a skeletonrepresented by the formula (1a);

FIG. 2 is a graph showing the result of transmittance measured on acoating layer of Polyimide precursor 1 synthesized in Example;

FIG. 3A is a graph showing the result of a dynamic viscoelasticitymeasurement on a film of Polyimide 1 synthesized in Example;

FIG. 3B is a graph showing the result of a dynamic viscoelasticitymeasurement on a film of Polyimide 3 synthesized in Example;

FIG. 4 is a graph showing the result of transmittance measured on eachcoating layer of Polyimide precursors 1, 3, 4 and 5 and Comparativeprecursors 1 and 2 synthesized in Example;

FIG. 5 is a graph showing the result of sensitivity measured onPhotosensitive resin composition 1 synthesized in Example; and

FIG. 6 is an opotical photomicrograph showing resolution ofPhotosensitive resin composition 1 synthesized in Example showingresolution.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the present invention will be explained in detail. Based ona totally novel concept, the inventor has designed a molecule ofpolyimide and has invented a polyimide precursor which is a precursor ofan aromatic polyimide having high heat resistance (particularlypreferably a wholly aromatic polyimide) and also has high transparencywithout introducing fluorine. That is, a concept to disconnect a πelectron conjugated structure of a molecular chain of a polyimideprecursor by introducing a mechanism to form an imide bond with an amidebond and a carboxylic acid and a derivative thereof respectively bondedto aromatic rings having a different π plane, and controlling aconfiguration of a skeleton is applied to polyimide.

Further, the present invention has been lead in the study of theinventor that the above-mentioned concept is not limited to thepolyimide precursor but can be widely applied to a polymer precursorcomprising a part which sequences an unsaturated bond having a πelectron orbit and a single bond alternately, and thereby having aconjugated state been easily formed in a molecule.

A polymer precursor of the present invention based on the above conceptis a polymer precursor comprising a polymer containing a part whichsequences an unsaturated bond having a π electron orbit and a singlebond alternately,

wherein the polymer precursor has a first functional group and a secondfunctional group which form a repeating unit constituting a polymerskeleton of an end product by an intramolecular reaction,

wherein at least a part of a conjugated state formed by the π electronorbit in the molecule is disconnected or weakened due to athree-dimensional structure of the molecule, and

wherein a transmittance with respect to an electromagnetic wave of atleast one wavelength selected from the group consisting of 436 nm, 405nm, 365 nm, 248 nm and 193 nm is larger than an expected transmittanceprovided that the conjugated state is under neither disconnectedcondition nor weakened condition.

In the polymer precursor of the present invention, at least a part ofthe conjugated state formed by the π electron orbit in the molecule isdisconnected or weakened by the three-dimensional structure of themolecule in the range of 0° C. to 50° C. Hence, the conjugated state canbe estimated and evaluated generally by a configuration at 20° C.

Since the polymer precursor of the present invention has a part whichsequences an unsaturated bond having a π electron orbit and a singlebond alternately, under normal circumstances, the conjugated state iseasily formed by the π electron orbit in the molecule and an electronorbit is stabilized, thereby, absorption tends to be exhibited at anelectromagnetic wave of a long wavelength.

In general, the π conjugated structure can be found when unsaturatedbonds are linked disposing a single bond therebetween. In that case, thesingle bond has a double bond-like property due to an interactionbetween unsaturated bonds. An electron (π electron) concerned in the πbond of the unsaturated bonds linked via the single bond is stabilizedby having a common π electron orbit. Hence, electrons including anelectron which is present on a bond originally of a single bond are inthe same plane.

The unsaturated bond in this a case is not limited to a bond betweencarbon atoms but also includes a hetero atom such as a carbonyl group orthe like.

Further, in the broad sense, a π conjugated structure, an unsaturatedbond of which is linked with a functional group comprising an atomhaving a noncovalent electron pair such as an amino group, an ethergroup or the like, may be exemplified as the π conjugated structure.

The present invention is applicable to all structures having a πconjugated structure heretofore known including the above-mentionedexamples.

As a typical example of the π conjugated structure, there may be anaromatic structure. An aromatic structure of the present invention meansa chemical structure generally defined as an aromatic series includingan aromatic cyclic structure in which unsaturated bonds in the structureare linked in a cyclic form and n-conjugated to form a planar structuresuch as benzene or naphthalene.

In the present invention, at least a part of the conjugated state whichwould be normally formed by a π electron orbit present in the moleculeof the polymer precursor is disconnected or weakened by thethree-dimensional structure of the molecule. Herein, the part in which aconjugated state would be normally formed is a part in which a doublebond containing a π bond and a single bond including only an σ bond aresequenced alternately when a planar primary structural formula of thepolymer precursor is drawn.

In this manner, stabilization of the π electron orbit present in themolecule of the polymer precursor is inhibited by disconnecting orweakening of at least a part of the conjugated state which would benormally formed. That is, a charge transfer in the molecule caused bythe unification of the π electron orbit is inhibited.

As a result, absorption in a long wavelength range vanishes or becomessmaller, hence, the polymer precursor exhibits high transmittance in ashorter wavelength range with respect to an electromagnetic wave.

The three-dimensional structure in the present invention includes bothconformation and configuration of a molecule. The conformation means aspatial arrangement of an atom or atomic group bonded to an asymmetriccarbon atom around the asymmetric carbon atom, or a spatial arrangementof an atom or atomic group bonded to a structure hard to move in amolecule around the structure, for example, a cis-trans isomer. Theconfiguration means various spatial arrangements of atoms in a moleculewhich is attained by rotation of two atomic groups linked by one singlebond in the molecule used as an axis.

The disconnecting or weakening of the π conjugated structure describedin the present invention means that an interaction of π electron orbitsbecomes not capable or difficult due to the effect of steric hindranceby introducing a substituent while normally unsaturated bonds are linkedvia a single bond so as to form a conjugated structure.

Specifically, it means the state that two π electron orbits ofunsaturated bonds located at both ends of a single bond are not in thesame plane. Generally, as an angle of the planes approaches from 0° to90°, an interaction becomes difficult to be exhibited. When the anglereaches 90°, it is considered to be most difficult to perform theinteraction.

Generally, it is considered that when two π electron orbits are on thesame plane, the interaction is most capable and they are stable, andwhen two π electron orbits cross at right angle, the interaction is mosttenuous and they are unstable. The stable electron orbit is excited byan electromagnetic wave of low energy, i. e. an electromagnetic wave oflong wavelength, thus absorption is large in that part. That is, thelarger the degree of inhabitation is against stabilization of the πelectron orbit, the further the absorption wavelength shifts to a shortwavelength side compared to the original absorption wavelength.

Herein, the effect of steric hindrance means that a tendency or drivingforce which forms a π plane, that is, a conjugated state, in order tostabilize or unify adjacent two or more π electron orbits due to athree-dimensional structure of a molecule and a tendency or drivingforce which increases stability of a conformation due to the cause otherthan the stabilization of the π electron orbit compete against eachother at a common position in the molecular structure so that theformation of the π plane is totally inhibited or the π plane isdistorted.

As a cause of the steric hindrance, there maybe, for example, adistortion of a cyclic structure or a spatial hindrance due to arelatively large substituent.

Whether a conjugated state in a molecule of a polymer compound will bedisconnected or weakened by a three-dimensional structure of themolecule can be presumed from the result of the molecular orbitalcalculation of the polymer compound or a similar model compound.

For example, 2,2′-dimethyl-4,4′-diaminobiphenyl corresponding to a modelcompound of the high transparency polyimide precursor as mentionedhereafter is difficult to be conjugated in comparison with4,4′-diaminobiphenyl to which a methyl group is not introduced since afree rotation of a single bond between benzene rings is inhibited by twomethyl groups introduced at the 2-position and 2′-position.

As aforementioned, a conjugated state of the polymer precursor isdisconnected or weakened, and as a result, absorption in a longwavelength range is vanished or becomes smaller so that a transmittancein a shorter wavelength with respect to an electromagnetic wave can beimproved.

Desirably, it is preferable that the polymer precursor of the presentinvention has at least a part of the conjugated state formed by the πelectron orbit in the molecule disconnected or weakened due to thethree-dimensional structure of the molecule so that a transmittance withrespect to an electromagnetic wave of at least one wavelength selectedfrom the group consisting of 436 nm, 405 nm and 365 nm is larger than anexpected transmittance provided that the conjugated state is underneither disconnected condition nor weakened condition since sensitivityof an emitting wavelength of a high-pressure mercury lamp utilized forexposure of a photosensitive resin or the like generally increases.

Herein, whether the transmittance with respect to an electromagneticwave of at least one wavelength selected from the group consisting of436 nm, 405 nm, 365 nm, 248 nm and 193 nm is larger than the expectedtransmittance provided that the conjugated state is under neitherdisconnected condition nor weakened condition can be confirmed bycomparing an approximate value of an absorption wavelength range and/orstrength which can be presumed from the calculation of a molecularmechanics or molecular orbital such as MM2, AM1 and PM5 of the polymerprecursor or a structure of a similar model compound having aconformation without a conjugated state disconnected and an actualmeasurement value thereof. As the similar model compound, for example,there may be a structure comprising a repeating unit of the polymerprecursor in which hydrogen is located on each end of the repeatingunit.

As other means, an absorption wavelength of a compound in which aconjugated structure is disconnected or weakened may be compared toconfirm with that of a model compound when the model compound of asimilar structure, in which a conjugated structure continues, stablyexists. For example, when conjugation stabilization is inhibited bysteric hindrance of the substituent introduced to the skeleton of thecompound, as the similar structure, there may be a structure having thesame skeleton but having a substituent substituted to a substituent ofsmaller steric hindrance (for example, hydrogen or the like).

If there is no compound to compare, a confirmation will suffice if atleast a state in which a π conjugated structure is disconnected and/orweakened is the most stable structure according to the calculation ofmolecular mechanics and molecular orbital, and the polymer precursor hasa transmittance of 20% or more with respect to an electromagnetic waveof at least one wavelength selected from the group consisting of 436 nm,405 nm, 365 nm, 248 nm and 193 nm when a film having a thickness of 1 μmusing the polymer precursor is formed or more simply when a film havinga thickness of about 1 μm to 5 μm using the polymer precursor is formed.That is, in the case that at least a part of a conjugated state form bya π electron orbit in a molecule is disconnected or weakened by athree-dimensional structure of a molecule, an energy level of theelectron orbit increases due to inhibiting stabilization of anelectronic state by the conjugated structure. Hence, only anelectromagnetic wave having larger energy (an electromagnetic wavehaving short wavelength) can be absorbed. As a result, absorption at along wavelength side due to an electron orbit having low energy levelvanishes from the absorption of the structure. Therefore, it can beconsidered that in comparison with the case provided that the conjugatedstate is not disconnected and weakened, generally, the state in whichthe Π conjugated structure is disconnected and/or weakened can transmitan electromagnetic wave of shorter wavelength, that is, a lightabsorption wavelength range shifts to the short wavelength side.

As aforementioned, since the polymer precursor of the present inventionhas at least a part of the conjugated state formed by the π electronorbit in the molecule disconnected or weakened due to athree-dimensional structure of the molecule, the polymer precursor ofthe present invention can transmit an electromagnetic wave of shorterwavelength than an electromagnetic wave which is transmitted through acompound having a similar structure in which the conjugated structurecontinues. In other words, a wavelength showing a certain transmittance(for example, an electromagnetic wave showing 20% of transmittance) ofthe polymer precursor of the present invention is shorter than that ofan electromagnetic wave which is transmitted through a compound having asimilar structure in which a conjugated structure continues. Theelectromagnetic wave has stronger energy when the wavelength is shorterand can be more easily absorbed by a compound. Hence, a wavelengthshowing a certain transmittance is shorter means that moreelectromagnetic waves are transmitted. Thereby, the polymer precursor ofthe present invention is high in transparency.

According to the present invention, excellent sensitivity can beobtained without declining useful properties in which the polymercompound, which is an end product derived from the polymer precursor,originally has in comparison with the case of increasing transmittanceof an electromagnetic wave by introducing other chemical structure or asubstituent such as fluorine or the like in the molecule.

According to the present invention, in the case that the polymerprecursor contains a considerable number of a part which sequences anunsaturated bond having a π electron orbit and a single bond alternatelyin the molecule, a transmittance can be 20% or more, preferably 30% ormore, more preferably 50% or more, particularly preferably 70% or morewith respect to an electromagnetic wave of at least one wavelengthselected from the group consisting of 436 nm, 405 nm, 365 nm, 248 nm and193 nm when a film having a thickness of 1 μm using the polymerprecursor is formed. It is preferable that a transmittance of thepolymer precursor is 20% or more, preferably 30% or more, morepreferably 50% or more, particularly preferably 70% or more, withrespect to an electromagnetic wave of all wavelength including 436 nm,405 nm and 365 nm when a film having a thickness of 1 μm using thepolymer precursor is formed.

The transmittance decreases as the film becomes thicker. Thus, effect ofhigh transparency of the polymer precursor of the present invention ismore apparent when the film is thick. It is further preferable that atransmittance of the polymer precursor of the present invention is 20%or more, preferably 30% or more, more preferably 50% or more, withrespect to an electromagnetic wave of at least one wavelength selectedfrom the group consisting of 436 nm, 405 nm, 365 nm, 248 nm and 193 nm,desirably with respect to an electromagnetic wave of all wavelengthincluding 436 nm, 405 nm and 365 nm, when a film having a thickness of 2μm or more, specifically 3 μm, 5 μm or 10 μm, using the polymerprecursor is formed.

If an aromatic structure, which is a typical example of a π conjugatedstructure, is abundantly contained in a molecule of a polymer precursor,a π conjugated chain of each aromatic structure tends to be unified toform a more stable conjugated state. The present invention is alsosignificantly effective to such a polymer precursor.

Specifically, a polymer precursor, wherein 50 wt % or more of the wholemolecular structure is an aromatic structure, is normally a typicalexample in which a conjugated state is likely to be formed by a πelectron orbit in a molecule. However, the polymer compound of thepresent invention can make a light absorption wavelength range be ashorter wavelength even if 50 wt % or more of the whole molecularstructure is an aromatic structure.

Herein, “50 wt % or more of the whole is an aromatic structure” meansthat a ratio of weight of a constitutional unit forming an aromaticstructure in a polymer is 50% or more in the total weight of thepolymer. The constitutional unit of an aromatic structure comprises anatom having a π electron concerned in an unsaturated bond forming anaromatic structure and a hydrogen atom or a halogen atom bonded directlyto the atom. Specifically, for example, in the case of xylene having achemical structure of CH₃—C₆H₄—CH₃, C₆H₄ is an aromatic structure. In achemical structure of CH₃—C₆Cl₄—CH₃, C₆Cl₄ is an aromatic structure.

A means to confirm whether 50 wt % or more of the whole is an aromaticstructure is not particularly limited. For example, a means such as a¹H- and ¹³C-NMR spectrum (nuclear magnetic resonance spectrum) of asolid or liquid, an infrared spectrum, a gas chromatography or the likecan be used.

Since in the case of containing a part which sequences an unsaturatedbond having a π electron orbit and a single bond alternately as a partof a polymer skeleton, a conjugated state is likely to be formed in along molecular chain in the molecule, the benefit which can be obtainedby apply the present invention to make absorption wavelength be ashorter wavelength thus increases.

From the above viewpoint, as a preferable embodiment of the presentinvention, there may be a polymer compound, wherein the part whichsequences an unsaturated bond having a π electron orbit and a singlebond alternately contains a chain structure of two or more repeatingunits which constitutes a polymer skeleton of the polymer precursor, andwherein a conjugated state is disconnected or weakened in the chainstructure.

Also, in the case of containing plural aromatic rings as a part of apolymer skeleton, the conjugated state is highly likely to be formed inthe molecule, hence, the benefit obtainable by improving transparency byapplying the present invention thus increases.

From the above viewpoint, as another embodiment of the presentinvention, there may be a polymer precursor, wherein 50% by mole or moreof repeating units constituting a polymer skeleton of the polymerprecursor is a repeating unit containing an aromatic ring or a condensedring containing an aromatic ring to be a part of the polymer skeleton ofthe polymer precursor, and wherein at least a part of a conjugated statebetween the aromatic rings or the condensed rings to be a part of thepolymer skeleton is disconnected or weakened due to a three-dimensionalstructure of the molecule.

In this case, a mole ratio of the three-dimensional structure of themolecule which disconnects or weakens the conjugated state is preferably50% or more with respect to an amount of the repeating unit containingthe aromatic ring or the condensed ring containing an aromatic ring tobe a part of the polymer precursor.

The polymer precursor of the present invention is a polymer and has afirst functional group and a second functional group which havereactivity and positional relationship to form a repeating unitconstituting a polymer skeleton of an end product by an intramolecularreaction.

As such a first functional group and second functional group, there maybe functional groups forming a ring structure to be a part of thepolymer skeleton by being bonded from each other due to anintramolecular ring closure reaction.

For example, if the first functional group is an amide group and thesecond functional group is a carboxyl group, a polyimide skeleton isformed. If the first functional group is an amide group and the secondfunctional group is a hydroxyl group, a polyoxazole skeleton is formed.If the first functional group is an amide group and the secondfunctional group is an amino group, a polyimidazole skeleton is formed.

A reaction in which an oxazole skeleton as a basic skeleton of thepolyoxazole skeleton is formed is represented by the following formula(5). Also, a reaction in which an imidazole skeleton as a basic skeletonof the polyimidazole skeleton is formed is represented by the followingformula (6).

The precursor compounds forming three kinds of skeletons haveelimination of water molecule or an alcohol molecule in accordance withan intramolecular ring closure reaction.

Mainly for a purpose requiring heat resistance, three compoundscontaining many aromatic skeletons are used. On the other hand, as manyaromatic structures are contained, a conjugated structure is caused,thereby, there is absorption in a long wavelength range, a transmittanceis low with respect to an exposure light source, and sensitivity is low.

From the viewpoint of storage stability of the polymer precursor, apolymer precursor, wherein the part which sequences an unsaturated bondhaving a π electron orbit and a single bond alternately has a first siteand a second site which are different from each other, wherein the firstfunctional group and the first site, and the second functional group andthe second site are respectively bonded directly or via other atom, andwherein the conjugated state formed between the first site and thesecond site is disconnected or weakened due to the three-dimensionalstructure of the molecule, is preferable.

In the case that the first functional group and the second functionalgroup are present on the same part which sequences an unsaturated bondhaving a π electron orbit and a single bond alternately, the firstfunctional group and the second functional group may be in the sameplane and fixed in a certain close positional relationship. Hence,storage stability may be deteriorated such as breaking of polymer chainor causing gelation as a side reaction proceeds in a state withoutadjusting reaction condition, for instance, a long-term storage or byheating. To the contrary, in the case that the conjugated state usuallyformed between the first site having the first functional group bondedand the second site having the second functional group bonded in themolecule is disconnected or weakened by the three-dimensional structureof the molecule, the first functional group and the second functionalgroup become three-dimensionally apart. Thus, the side reaction isinhibited from proceeding upon storage. As a result, storage stabilityof the polymer precursor improves. When it is necessary to derive thepolymer precursor to the polymer compound, which is an end product, onlyan intramolecular reaction required originally can be proceeded byadjusting a reaction condition.

As an example, there may be a polymer precursor, wherein the part whichsequences an unsaturated bond having a π electron orbit and a singlebond alternately contains at least two aromatic rings, wherein the firstsite is present at a first aromatic ring of the aromatic rings and thesecond site is present at a second aromatic ring of the aromatic rings,and wherein the conjugated state formed between the first aromatic ringand the second aromatic ring is disconnected or weakened due to thethree-dimensional structure of the molecule.

As a more specific example, the polymer precursor is a polyimideprecursor comprising a repeating unit derived from acid anhydride havingan anhydride group formed with carboxyl groups bonded to aromatic ringshaving different π plane directly or via other atom. In such a case,storage stability improves since a reverse reaction from the precursorto the acid anhydride is inhibited.

The polymer precursor of the present invention has excellent storagestability by controlling a three-dimensional structure so that thereverse reaction is hard to proceed. Specifically, preferable storagestability is a rate of change of 20% or less, preferably 10% or less,more preferably 5% or less, in terms of the polystyrenecalibrated-weight average molecular weight by gel permeationchromatography (GPC) of a 0.5 wt % solution of the polymer precursor ina good solvent which can dissolve the polymer precursor by 0.5 wt % ormore and substantially contains water after stored at 23° C. for 25hours. Further, it is also preferable that rates of change is 20% orless, preferably 10% or less, more preferably 5% or less, in terms ofthe polystyrene calibrated-weight average molecular weight by gelpermeation chromatography after storing the above 0.5 wt % solution at23° C. for 50 hours, 150 hours and 300 hours. Herein, the rate of changeof weight average molecular weight means a difference between weightaverage molecular weights before and after storing with respect to aweight average molecular weight before storing (a difference betweenweight average molecular weights before and after storing/a weightaverage molecular weight before storing). “Substantially containingwater” means a state without dehydration when the above-mentioned goodsolvent has property that it is likely to contain water in the air, andmeans a state having a percentage of water content in the solvent ofabout 0.001 wt % to 10 wt %, further about 0.005 wt % to 1 wt %.

If the part which sequences an unsaturated bond having a π electronorbit and a single bond alternately contains the chain structure of twoor more repeating units constituting the polymer skeleton of the polymerprecursor, the first aromatic ring having the first functional group andthe second aromatic ring having the second functional group may becontained in different repeating units, and the conjugated state may bedisconnected or weakened due to the three-dimensional structure of themolecule in the polymer skeleton connecting the first aromatic ring andthe second aromatic ring.

Also, if the part which sequences an unsaturated bond having a πelectron orbit and a single bond alternately is contained in the samerepeating unit constituting the polymer skeleton of the polymerprecursor, the first aromatic ring having the first functional group andthe second aromatic ring having the second functional group may becontained in the same repeating unit, and the conjugated state maybedisconnected or weakened due to the three-dimensional structure of themolecule at any position in the repeating unit.

In this case, it is preferable that 50% by mole or more of the repeatingunit constituting the polymer skeleton of the polymer precursor is arepeating unit containing both first aromatic ring having the firstfunctional group and second aromatic ring having the second functionalgroup.

The aforementioned polymer precursor of the present invention can beused as a resin material for forming various coating layers having apattern or a form, products or members as it is or by mixing with othercomponents to prepare a precursor resin composition. Particularly, thepolymer precursor of the present invention is suitably used as aphotosensitive resin since absorption of an electromagnetic wave isshifted to a shorter wavelength range so as to improve a transmittanceof an electromagnetic wave of a long wavelength range.

As a method to use the polymer precursor of the present invention as aphotosensitive resin, there may be a method to introduce aphotosensitive portion which cures the polymer precursor itself orchanges solubility of the polymer precursor itself when irradiated withradiations having a wavelength of 440 nm or less in the molecule of thepolymer precursor.

As other method, there may be a method to introduce a reactive portion(that is, an indirect photosensitive portion) which exhibits effect thatthe polymer precursor itself is cured or solubility of the polymerprecursor itself is changed due to activation by effect of a compoundhaving absorption in an electromagnetic wave having a wavelength of 440nm or less in the molecule of the polymer precursor.

Also, as other method, a photosensitive polymer precursor resincomposition prepared by mixing the above-mentioned polymer precursor nothaving the photosensitive portion introduced with the above-mentionedphotosensitive component having the photosensitive portion may be used.

Further, a photosensitive polymer precursor resin composition preparedby mixing the polymer precursor having the photosensitive portionintroduced with the photosensitive component may be used.

A coating layer containing a polymer compound or a resin compositioncontaining the polymer compound in a predetermined pattern form can beobtained in such a manner that after a coating layer of such aphotosensitive polymer precursor resin composition is exposed withradiations, particularly an electromagnetic wave, of a predeterminedwavelength followed by a predetermined operation if required anddevelopment, the first functional group and the second functional groupof the polymer precursor are subject to an intramolecular reaction byheating or the effect of catalyst so as to be converted to a polymercompound, which is an end product.

Hereafter, a high transparency polyimide precursor is explained indetail as an example of the polymer precursor of the present invention.Hereafter, properties, advantage and other contents of the hightransparency polyimide precursor to be explained are, if notparticularly conflictive, common explanation of the polymer precursor ofthe present invention in general.

The high transparency polyimide precursor of the present invention has arepeating unit represented by the formula (1a) or (1b) or has bothrepeating units represented by the following formulae (1a) and (1b), andis a precursor of polyimide containing a seven-membered ring imidestructure as an end product:

wherein, each of R¹ to R⁶ is independently a hydrogen atom or amonovalent organic group, which may be bonded each other; each of R⁷ andR⁸ is independently a hydrogen atom or a monovalent organic group; “X”is a divalent organic group; each of R⁹ and R¹⁰ is independently ahydrogen atom or a monovalent organic group; and groups represented bythe same symbol among repeating units in the same molecule maybedifferent atoms or structures.

A polyimide precursor derived from an aromatic five-membered ringdianhydride represented by the polyimide precursor derived frompyromellitic dianhydride and a polyimide precursor having an aromaticsix-membered ring dianhydride structure represented by a polyimideprecursor derived from 1,4,5,8, -naphthalene tetracarboxylic dianhydridehave carbonyl groups finally forming an imide bond in the same π plane,thus, a conjugated structure of a π electron tends to spread over amolecular chain of the polyimide precursor.

Since a polyimide precursor derived from3,3′,4,4′-biphenyltetracarboxylic dianhydride also has an amide groupand a carboxyl group capable of an intramolecular ring closure reactionbonded to the same benzene ring, positions of two kinds of substituentsare fixed, thus, a reverse reaction is likely to proceed.

Also, since a single bond connecting two benzene rings derived from acidanhydride can freely rotate, and a π conjugation structure can be formedby the benzene rings, a transmittance of an electromagnetic wave in alow wavelength range is often low.

Since a polyimide precursor derived from2,2′,3,3′-biphenyltetracarboxylic dianhydride also has an amide groupand a carboxyl group capable of an intramolecular ring closure reactionbonded to the same benzene ring, a reverse reaction is likely toproceed.

Also, as for the polyimide precursor derived from2,2′,3,3′-biphenyltetracarboxylic dianhydride, two aromatic ringsderived from acid anhydride is less likely to conjugatethree-dimensionally. However, polyimide derived from the precursor ishighly colored due to a five-membered ring imide structure, and furthercoefficient of expansion is less likely to decrease since a molecularchain has a flexuous structure. Hence, an applicable usage of thepolyimide is limited.

Particularly, in the case of wholly aromatic polyimide using not onlyaromatic acid dianhydride as an acid component but also aromatic diamineas a diamine component, the conjugated structure is more likely tospread over the molecular chain of polyimide in wide range, thus, it ismore likely to cause a coloring phenomenon.

On the contrary, the repeating unit represented by the formula (1a) or(1b) has a structure derived from 2,2′,6′,6′-biphenyltetracarboxylicdianhydride or a compound having a substituent on its aromatic ring, andis three-dimensionally unstable when two aromatic rings derived fromtetracarboxylic acid are arranged in a plane. Hence, a relative positionof benzene rings of the biphenyl structure contained in the polyimideprecursor is twisted so that a conjugation of a π bond is disconnected.

FIG. 1 shows a spatial arrangement presumed from the result of the MM2molecular orbital calculation of a model compound having a skeleton ofthe formula (1a) represented by the following formula:

Since a bond which bonds benzene rings of the biphenyl skeleton of2,2′,6,6′-biphenyltetracarboxylic dianhydride can rotate, a reaction isperformed with amine to be a polyimide precursor. Thus, it is assumedfrom the result of the MM2 molecular orbital calculation that twobenzene rings are not present in the same plane due to steric hindrance,but have a configration that run at right angles to each other.

Since the high transparency polyimide precursor of the present inventionhas such a spatial arrangement of the molecular structure, the polyimideprecursor has the π conjugation on the molecular chain of the polyimideprecursor inhibited so that the absorption wavelength becomes a shorterwavelength while maintaining heat resistance of aromatic polyimide in afinal imidized product.

Also, since the reverse reaction is less likely to proceed in the hightransparency polyimide precursor of the present invention, excellentstorage stability is also exhibited. Further, since2,2′,6,6′-biphenyltetracarboxylic dianhydride, which is a startingmaterial, can be obtained by a relatively simple synthesis method suchas an oxidation reaction of pyrene or the like, it is available at a lowprice.

The polyimide precursor which is produced using2,2′,6,6′-biphenyltetracarboxylic dianhydride has been conventionallyknown, however, the physical properties thereof have not been known indetail. Particularly, properties of good transparency and storagestability have not ever known at all.

It is found by the present invention that a polyimide precursor which isproduced using 2,2′,6,6′-biphenyltetracarboxylic dianhydride based on anovel molecular design to enhance transparency of the polyimideprecursor has a good transparency due to a mechanism in which aconventional high transparency polyimide precursor does not have. Thepresent invention shows suitable applications of the polyimide precursorin the field which can utilize its high transparency as well as originalproperties of the polyimide precursor.

In the repeating unit represented by the formula (1a) or (1b), asubstituent other than a hydrogen atom may be introduced at the positionof R¹ to R⁶. If the repeating unit represented by the formula (1a) or(1b) of the polyimide precursor of the present invention has a skeletonderived from 2,2′,6,6′-biphenyltetracarboxylic dianhydride, transparencyimproves. Thus, even the substituents are introduced to R¹ to R⁶, asimilar effect can be expected.

As a monovalent organic group which can be introduced to R¹ to R⁶ otherthan a hydrogen atom, there may be, for example, a halogen atom, ahydroxyl group, a mercapto group, a primary amino group, a secondaryamino group, a tertiary amino group, a cyano group, a silyl group, asilanol group, an alkoxy group, a nitro group, a carboxyl group, anacetyl group, an acetoxy group, a sulfo group, a saturated orunsaturated alkyl group, a saturated or unsaturated halogenated alkylgroup, an aromatic group such as phenyl, naphthyl or the like, an allylgroup or the like. R¹ to R⁶ may be the same or different from eachother. Two or more groups among R¹ to R⁶, particularly, two or threegroups among R¹ to R³ and/or two or three groups among R⁴ to R⁶ may bebonded each other to form a ring structure.

The substituents R¹ to R⁶ may be introduced in a state of a startingmaterial so that a state of acid dianhydride has the substituentsalready introduced, or may be reacted with diamine so as to introduce itin a state of polyimide or polyamic acid. Also, a wavelength of light tobe absorbed can be adjusted by introducing a substituent, hence, adesired wavelength can be absorbed by introducing a substituent.

As a guide to determine kinds of substituent to be introduced in orderto shift an absorption wavelength with respect to a desired wavelength,A. I. Scott, Interpretation of the Ultraviolet Spectra of NaturalProducts, 1964, or a table in R. M. Silverstein, Identification ofOrganic Compound by Spectrum, 5^(th) edition, 1993, may be of reference.

“X” in each of the formula (1a) and the formula (1b) is a divalentorganic group. There may be, for example, a divalent organic group whichcorresponds to each diamine component to be hereinafter described, thatis, a structure comprising a diamine component without amino groups ofboth ends which are concerned in formation of a polyimide chain. Betweeneach repeating unit which is present in the same polyimide chain, groupsrepresented by the same symbol may be different atoms or structures.

R⁷ and R⁸ in the formula (1a) or (1b) are a hydrogen atom and/or amonovalent organic group. Specifically, as the monovalent organic group,for example, there may be a hydroxyl group, a halogen atom, a mercaptogroup, a primary amino group, a secondary amino group, a tertiary aminogroup, a cyano group, a silyl group, a silanol group, an alkoxy group, anitro group, a carboxyl group, an acetyl group, an acetoxy group, asulfo group, a saturated or unsaturated alkyl group, a saturated orunsaturated halogenated alkyl group, an aromatic group such as phenyl,naphthyl or the like, an allyl group, an ethylenically unsaturated bondcontaining group or the like. R⁷ and R⁸ may be the same or differentfrom each other. Various kinds of R⁷ and R⁸ may be mixed in eachrepeating unit.

The ethylenically unsaturated bond containing group means a substituenthaving one or more ethylenically unsaturated bonds. Specifically, forexample, there may be an allyloxy group, a 2-acryloyloxyethyloxy group,a 2-methacryloyloxypropyloxy group, a 2-acryloyloxyethylamino group, a2-methacryloyloxyethylamino group, a 2-acryloyloxypropylamino group, a2-hydroxy-3-methacryloyloxyproloxy group, a2-hydroxy-3-acryloyloxypropyloxy group, a 2-hydroxy-4-pentenyloxy group,a 2-acryloyloxyethyl dimethylammonium group, a 2-methacryloyloxypropyltrimethylammonium group, or a derivative thereof.

R⁹ and R¹⁰ are independently a hydrogen atom and/or a monovalent organicgroup. Specifically, for example, there may be a hydroxyl group, ahalogen atom, a mercapto group, a primary amino group, a secondary aminogroup, a tertiary amino group, a cyano group, a silyl group, a silanolgroup, an alkoxy group, a nitro group, a carboxyl group, an acetylgroup, an acetoxy group, a sulfo group, a saturated or unsaturated alkylgroup, a saturated or unsaturated halogenated alkyl group, an aromaticgroup such as phenyl, naphthyl or the like, an allyl group, anethylenically unsaturated bond containing group or the like. R⁹ and R¹⁰may be the same or different from each other. Various kinds of R⁹ andR¹⁰ may be mixed in each repeating unit.

As for the high transparency polyimide precursor of the presentinvention, from the viewpoint of enhancing heat resistance anddimensional stability of polyimide to be finally obtained, it ispreferable to use a wholly aromatic polyimide precursor in which aportion derived from acid dianhydride has an aromatic structure andfurther a portion derived from diamine has also an aromatic structure.Therefore, it is preferable that “X”, which is a structure derived froma diamine component, is a structure derived from aromatic diamine.Herein, the wholly aromatic polyimide precursor means a polyimideprecursor obtainable from copolymerization of an aromatic acid componentand an aromatic amine component or polymerization of aromatic acid/aminecomponent. Also, the aromatic acid component means a compound having allfour acidic groups forming a polyimide skeleton are substituted onaromatic rings. The aromatic amine component means a compound havingboth of two amino groups forming a polyimide skeleton are substituted onaromatic rings. The aromatic acid/amine component means a compoundhaving both acidic group and amino group forming a polyimide skeletonsubstituted on aromatic rings. As it is clear from examples of astarting material to be hereinafter described, not all acidic groups oramino groups are necessary to be present on the same aromatic ring.

The solubility of the high transparency polyimide precursor of thepresent invention may also be improved by introducing a substituent inthe molecular structure. From this point of view, it is preferable thatR¹ to R⁶ of the above-mentioned substituent is selected from the groupconsisting of a saturated and unsaturated alkyl group having 1 to 15carbons, a saturated and unsaturated alkoxy group having 1 to 15carbons, a bromo group, a chloro group, a fluoro group, a nitro group, aprimary to tertiary amino groups and the like. Also, these groups may bepresent at the divalent organic group “X”.

The high transparency polyimide precursor of the present invention maycontain a repeating unit other than the formula (1a) or (1b) as far asthe object of the present invention, which is to improve properties suchas transparency, heat resistance, dimensional stability or the like ofpolyimide to be finally obtained, can be attained.

For example, the polyimide precursor of the present invention maycontain a repeating unit having a structure other than the formula (1a)or (1b), or a repeating unit which is not an imide structure such as arepeating unit of an amide structure (a repeating unit of polyamide).

As the repeating unit having a structure other than the formula (1a) or(1b), there may be, for example, a repeating unit represented by thefollowing formula (2):

wherein, each of R¹¹ and R¹² is independently a hydrogen atom or amonovalent organic group; each of R¹³ and R¹⁴ is independently ahydrogen atom or a monovalent organic group; “Y” is a tetravalentorganic group; “Z” is a divalent organic group; and groups representedby the same symbol among repeating units in the same molecule may bedifferent atoms or structures.

Polyimide containing a repeating unit represented by the formula (1a)and/or (1b) and a repeating unit represented by the formula (2) may berepresented by the following formula (3). The polyimide represented bythe formula (3) may contain a repeating unit other than the formula (1a)and/or (1b) and the formula (2):

wherein, in the formula (3), each symbol is the same as in the formula(1a) and/or (1b) or the formula (2); among repeating units present inthe same molecule, groups represented by the same symbol may bedifferent atoms or structures; at least one of “o” and “p” is a naturalnumber of 1 or more and “o”, “p” and “q” are natural numbers of 0 ormore; and each unit of the formula (1a), the formula (1b) and theformula (2) may be a random arrangement or an arrangement withregularity.

The imide structure other than the formula (1a) or (1b) may beintroduced into a polyimide precursor chain by using acid dianhydrideother than 2,2′,6,6′-biphenyltetracarboxylic dianhydride or a derivativethereof.

As a production method of producing the polyimide precursor of thepresent invention, conventional methods can be applied, for example, butmay not be limited thereto:

(1) a method wherein acid dianhydride and diamine are synthesized toobtain polyamic acid, which is a precursor; and

(2) a method wherein a polyimide precursor is synthesized by reactingcarboxylic acid of ester acid or amide acid monomer synthesized byreacting dianhydride with a monovalent alcohol an amino compound, anepoxy compound or the like with a diamino compound or a derivativethereof.

As aforementioned, as acid dianhydride used herein, not only2,2′,6,6′-biphenyltetracarboxylic dianhydride but also a derivativepreliminary having a substituent introduced at one or more of R¹ to R⁶according to the purpose. As the acid dianhydride, acid dianhydrideother than 2,2′,6,6′-biphenyltetracarboxylic dianhydride and/or thederivative thereof may be used together. Two or more of2,2′,6,6′-biphenyltetracarboxylic dianhydride and/or the derivativethereof and other acid dianhydrides may be used together as far aspolyimide precursor has transparency.

As the acid dianhydride which can be used together with2,2′,6,6′-biphenyltetracarboxylic dianhydride and/or the derivativethereof, aromatic acid dianhydride is preferable from the viewpoint of aheat resistance. According to desired physical properties, aciddianhydride other than 2,2′,6,6′-biphenyltetracarboxylic dianhydride maybe used within 50% by mole, preferably 30% by mole, of the whole amountof acid dianhydride.

As other acid dianhydride which can be used together with2,2′,6,6′-biphenyltetracarboxylic dianhydride and/or the derivatives atthe same time, there may be, for example, ethylenetetracarboxylicdianhydride, butanetetracarboxylic dianhydride,cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylicdianhydride, pyromellitic dianhydride,3,3′,4,4′-benzophenonetetracarboxylic dianhydride,2,2′,3,3′-benzophenonetetracarboxylic dianhydride,3,3′,4,4′-biphenyltetracarboxylic dianhydride,2,2′,3,3′-biphenyltetracarboxylic dianhydride,2,2-bis(3,4-dicarboxyphenyl)propane dianhydride,2,2-bis(2,3-dicarboxyphenyl)propane dianhydride,bis(3,4-dicarboxyphenyl)ether dianhydride,bis(3,4-dicarboxyphenyl)sulfone dianhydride,1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride,bis(2,3-dicarboxyphenyl)methane dianhydride,bis(3,4-dicarboxyphenyl)methane dianhydride,2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride,2,2-bis(2,3-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride,1,3-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride,1,4-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride,2,2-bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}propane dianhydride,2,2-bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}propane dianhydride,bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride,bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride,4,4′-bis[4-(1,2-dicarboxy)phenoxy]biphenyl dianhydride,4,4′-bis[3-(1,2-dicarboxy)phenoxy]biphenyl dianhydride,bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride,bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride,bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride,bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride,bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}sulfido dianhydride,bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfido dianhydride,2,2-bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}-1,1,1,3,3,3-hexafuloropropanedianhydride,2,2-bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}-1,1,1,3,3,3-propanedianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride,1,4,5,8-naphthalenetetracarboxylic dianhydride,1,2,5,6-naphthalenetetracarboxylic dianhydride,1,2,3,4-benzenetetracarboxylic dianhydride,3,4,9,10-perylenetetracarboxylic dianhydride,2,3,6,7-anthracenetetracarboxylic dianhydride,1,2,7,8-phenanthrenetetracarboxylic dianhydride or the like. They may beused solely or in a mixture of two or more kinds. As tetracarboxylicdianhydride which may be used particularly preferably, there may bepyromellitic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylicdianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride,bis(3,4-dicarboxyphenyl)ether dianhydride, or 2,2-bis(3,4-dicarboxyphenyl) -1,1,1,3,3 3-hexafluoropropane dianhydride.

If acid dianhydride having fluorine introduced or acid dianhydridehaving an alicyclic skeleton is used as acid dianhydride for usingtogether, physical properties such as solubility, thermal expansioncoefficient of finally obtainable polyimide or the like can be adjustedwithout appreciable decline in transparency. Also, if a rigid aciddianhydride such as pyromellitic anhydride,3,3′,4,4′-biphenyltetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride or the like is used, the coefficient oflinear thermal expansion of finally obtainable polyimide decreases.However, the rigid acid dianhydride tends to inhibit improvement oftransparency, thus may be used together caring about copolymerizationratio according to the purpose.

On the other hand, one kind of diamine may be solely used or two or morekinds of diamine may be used together for an amine component. As usablediamines, there may be, but may not be limited thereto,p-phenylenediamine, m-phenylenediamine, o-phenylenediamine,3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether,4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfido,3,4′-diaminodiphenyl sulfido, 4,4′-diaminodiphenyl sulfido,3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone,4,4′-diaminodiphenyl sulfone, 3,3′-diaminobenzophenone,4,4′-diaminobenzophenone, 3,4′-diaminobenzophenone,3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane,3,4′-diaminodiphenylmethane, 2,2-di(3-aminophenyl)propane,2,2-di(4-aminophenyl)propane,2-(3-aminophenyl)-2-(4-aminophenyl)propane,2,2-di(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane,2,2-di(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane,2-(3-aminophenyl)-2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoro propane,1,1-di(3-aminophenyl)-1-phenylethane,1,1-di(4-aminophenyl)-1-phenylethane,1-(3-aminophenyl)-1-(4-aminophenyl)-1-phenylethane,1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene,1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene,1,3-bis(3-aminobenzoyl)benzene, 1,3-bis(4-aminobenzoyl)benzene,1,4-bis(3-aminobenzoyl)benzene, 1,4-bis(4-aminobenzoyl)benzene,1,3-bis(3-amino-α,α-dimethylbenzyl)benzene,1,3-bis(4-amino-α,α-dimethylbenzyl)benzene,1,4-bis(3-amino-α,α-dimethylbenzyl)benzene,1,4-bis(4-amino-α,α-dimethylbenzyl)benzene,1,3-bis(3-amino-α,α-ditrifluoromethylbenzyl)benzene,1,3-bis(4-amino-α,α-ditrifluoromethylbenzyl)benzene,1,4-bis(3-amino-α,α-ditrifluoromethylbenzyl)benzene,1,4-bis(4-amino-α,α-ditrifluoromethylbenzyl)benzene,2,6-bis(3-aminophenoxy)benzonitrile, 2,6-bis(3-aminophenoxy)pyridine,4,4′-bis(3-aminophenoxy)biphenyl, 4,4′-bis(4-aminophenoxy)biphenyl,bis[4-(3-aminophenoxy)phenyl]ketone,bis[4-(4-aminophenoxy)phenyl]ketone,bis[4-(3-aminophenoxy)phenyl]sulfido,bis[4-(4-aminophenoxy)phenyl]sulfido,bis[4-(3-aminophenoxy)phenyl]sulfone,bis[4-(4-aminophenoxy)phenyl]sulfone,bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether,2,2-bis[4-(3-aminophenoxy)phenyl]propane,2,2-bis[4-(4-aminophenoxy)phenyl]propane,2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane,2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane,1,3-bis[4-(3-aminophenoxy)benzoyl]benzene,1,3-bis[4-(4-aminophenoxy)benzoyl]benzene,1,4-bis[4-(3-aminophenoxy)benzoyl]benzene,1,4-bis[4-(4-aminophenoxy)benzoyl]benzene,1,3-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene,1,3-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene,1,4-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene,1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene,4,4′-bis[4-(4-aminophenoxy)benzoyl]diphenylether,4,4′-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone,4,4-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone,4,4′-bis[4-(4-aminophenoxy)phenoxy]diphenylsulfone,3,3-diamino-4,4′-diphenoxybenzophenone,3,3-diamino-4,4′-dibiphenoxybenzophenone,3,3′-diamino-4-phenoxybenzophenone,3,3′-diamino-4-biphenoxybenzophenone,6,6′-bis(3-aminophenoxy)-3,3,3′,3′-tetramethyl-1,1′-spirobiindane,6,6′-bis(4-aminophenoxy)-3,3,3′,3′-tetramethyl-1,1′-spirobiindane,1,3-bis(3-aminopropyl)tetramethyldisiloxane,1,3-bis(4-aminobutyl)tetramethyldisiloxane,α,ω-bis(3-aminopropyl)polydimethylsiloxane,α,ω-bis(3-aminobutyl)polydimethylsiloxane, bis(aminomethyl)ether,bis(2-aminoethyl)ether, bis(3-aminopropyl)ether,bis(2-aminomethoxy)ethyl]ether, bis[2-(2-aminoethoxy)ethyl]ether,bis[2-(3-aminoprotoxy)ethyl]ether, 1,2-bis(aminomethoxy)ethane,1,2-bis(2-aminoethoxy)ethane, 1,2-bis[2-(aminomethoxy)ethoxy]ethane,1,2-bis[2-(2-aminoethoxy)ethoxy]ethane, ethylene glycolbis(3-aminopropyl)ether, diethylene glycol bis(3-aminopropyl)ether,triethylene glycol bis(3-aminopropyl)ether, ethylenediamine,1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane,1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane,1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane,1,12-diaminododecane, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane,1,4-diaminocyclohexane, 1,2-di (2-aminoethyl)cyclohexane, 1,3-di(2-aminoethyl)cyclohexane, 1,4-di (2-aminoethyl)cyclohexane,bis(4-aminocyclohexyl)methane,2,6-bis(aminomethyl)bicyclo[2,2,1]heptane, or2,5-bis(aminomethyl)bicyclo[2,2,1]heptane. Also, diamine in which a partor all of the hydrogen atoms on the aromatic ring of the above-mentioneddiamine is substituted by a substituent selected from the groupconsisting of a fluoro group, a methyl group, a methoxy group, atrifluoromethyl group, or a trifluoromethoxy group can also be used.Moreover, according to the purpose, diamine in which a part or all ofthe hydrogen atoms on the aromatic ring has one or more groups among anethynyl group, a benzocyclobutene-4′-yl group, a vinyl group, an allylgroup, a cyano group, an isocyanate group and an isopropenyl group to becrosslinked points introduced as a substituent can also be used.

Diamine can be selected according to the desired physical property. Whenrigid diamine such as p-phenylenediamine or the like is used, thecoefficient of expansion of polyimide derived from the high transparencypolyimide precursor becomes low.

As rigid diamine in which two amino groups bonds together to the samearomatic ring, there may be p-phenylenediamine, m-phenylenediamine,1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene,2,7-diaminonaphthalene, 1,4-diaminoanthracene or the like.

Further, there may be diamine in which two or more aromatic rings arebonded by single bonds and two or more amino groups are respectivelybonded on a different aromatic ring directly or as a part of asubstituent. For example, the following formula (4) may be exemplified.Specifically, there may be benzidine or the like:

wherein, “a” is a natural number of 1 or more; and the amino groups arebonded in a para or meta position with respect to the bond between thebenzene rings.

Further, in the formula (4), diamine having substituents which are notconcerned in bonding with other benzenes at positions of the benzenerings where no amino group is substituted may be used. The substituentsare monovalent organic groups, which may be bonded each other.

Specifically, for example, there may be2,2′-dimethyl-4,4′-diaminobiphenyl,2,2′-ditrifluoromethyl-4,4′-diaminobiphenyl,3,3′-dichloro-4,4′-diaminobiphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl,3,3′-dimethyl-4,4′-diaminobiphenyl or the like.

Also, in the case of using the polyimide precursor and polyimide derivedtherefrom of the present invention as an optical waveguide or an opticalcircuit part, a transmittance with respect to an electromagnetic wavehaving a wavelength of 1 μm or more can be improved if fluorine isintroduced as a substituent of the aromatic ring.

On the other hand, if diamine having a siloxane skeleton such as1,3-bis(3-aminopropyl)tetramethyl disiloxane or the like is used asdiamine, an elastic modulus decreases and the glass transitiontemperature can be lowered of the polyimide precursor and polyimidederived therefrom of the present invention.

Herein, aromatic diamine is preferably selected as the diamine from theviewpoint of heat resistance. Diamine other than aromatic series such asaliphatic diamine, siloxane based diamine or the like maybe also usedaccording to the desired physical properties within 60% by mole,preferably 40% by mole, of the whole amount of diamine.

Next, a synthesizing method of 2,2′,6,6′-biphenyltetracarboxylicdianhydride which is a starting material of the high transparencypolyimide precursor of the present invention and a synthesis method ofthe high transparency polyimide precursor will be hereinafter describedin detail, however, the present invention is not limited thereto.

2,2′,6,6′-biphenyltetracarboxylic dianhydride, which has the most basicstructure among acid component materials, can be obtained by anoxidation reaction of pyrene. That is, firstly, pyrene is solved indichloromethane. After solving the pyrene completely, acetonitrile andwater are added and agitated. Sodium periodate as an oxidizer andruthenium trichloride as a catalyst are added thereto followed byagitation for 10 to 30 hours at room temperature. After reaction, aprecipitate is filtered. The precipitate is extracted with acetonefollowed by filtering. The acetone used for extraction is concentratedfollowed by drying, and refluxed by dichloromethane for 4 to 10 hoursfollowed by filtering. The obtained white solid is2,2′,6,6′-biphenyltetracarboxylic acid, which is a precursor of2,2′,6,6′-biphenyltetracarboxylic dianhydride. After the obtained2,2′,6,6′-biphenyltetracarboxylic acid is refluxed with acetic anhydridefor 3 hours, a solvent is distilled away. The obtained solid matter isrefined by sublimation under the condition of 0.8 mmHg (106.4 Pa)pressure and 230° C., thus obtained a desired2,2′,6,6′-biphenyltetracarboxylic dianhydride.

Next, an example of synthesis of the polyimide precursor using theabove-mentioned 2,2′,6,6′-biphenyltetracarboxylic dianhydride as an acidcomponent and 4,4′-diamino diphenyl ether as an amine component will beexplained. First, equimolar 2,2′,6,6′-biphenyltetracarboxylicdianhydride is gradually added to an organic polar solvent such asN-methylpyrrolidone or the like having 4,4′-diamino diphenyl ethersolved while cooling followed by agitation caring that the temperatureof the reaction solution will not rise.2,2′,6,6′-biphenyltetracarboxylic dianhydride generates heat whenreacted with an amino compound more than pyromellitic dianhydride or3,3′,4,4′-biphenyltetracarboxylic dianhydride. This is presumed thatsince the reaction of 2,2′,6,6′-biphenyltetracarboxylic dianhydride isgood, proceeding of the reaction is fast. Hence, since an acid anhydridegroup is likely to react with moisture to be dicarboxylic acid, thereaction is preferably performed in dehydrated state in order to obtaina high molecular weight polyimide precursor.

If a temperature of the reaction solvent is as low as possible but notlower than the freezing point of the solvent, a high molecular weightpolymer can be obtained. It is preferable that the temperature does notbecome 80° C. or more, particularly preferably 40° C. or more, duringthe reaction. It is also preferable to maintain the temperature at 10°C. or less in order to obtain a high molecular weight polymer having amolecular weight of 10,000 or more.

After about 1 to 20 hours of agitation while cooling, a reactionsolution is dropped into agitated and dehydrated diethyl ether toreprecipitate, thereby, polyamic acid, which is a polyimide precursor,is obtained. The polyamic acid is again dissolved to an organic polarsolvent such as N-methylpyrrolidone or the like and applied on asubstrate such as a glass or the like to dry, thereby, a coating layerof polyamic acid is formed. Then, after heating, a coating layer ofpolyimide is obtained.

Also, in the case of performing a chemical imidization instead of theheating and dehydration, a conventional compound including amine such aspyridine, β-picolinic acid or the like, carbodiimide such asdicyclohexylcarbodiimide or the like, acid anhydride such as aceticanhydride or the like may be used as a dehydration catalyst. As the acidanhydride, there may be not only the acetic anhydride but also propionicanhydride, n-butyric anhydride, benzoic anhydride, trifluoroaceticanhydride or the like, but may not be particularly limited. Also,tertiary amine such as pyridine, β-picolinic acid or the like may beused together.

As for the polyimide precursor of the present invention as synthesizedabove, in order to make excellent original heat resistance anddimensional stability of polyimide finally obtained, it is preferablethat a copolymerization ratio of an aromatic acid component and/or anaromatic amine component is as large as possible. Specifically, it ispreferable that a ratio of the aromatic acid component with respect toan acid component constituting the repeating unit of the imide structureis 50% by mole or more, particularly 70% by mole or more. It ispreferable that a ratio of the aromatic amine component with respect tothe amine component constituting the repeating unit of the imidestructure is 40% by mole or more, particularly 60% bymole or more . Awholly aromatic polyimide is particularly preferable.

From the viewpoint of attaining transparency, it is preferable that inthe high transparency polyimide precursor of the present invention, 50%by mole or more, particularly 70% by mole or more, of the repeating unitof the polyimide precursor structure present in the polymer skeleton isthe repeating unit represented by the formula (1a) or (1b). Also, fromthe viewpoint of heat resistance and dimensional stability, it ispreferable that the repeating unit represented by the formula (1a) or(1b) is a repeating unit of the wholly aromatic polyimide precursor.

The polyimide precursor of the present invention synthesized as abovehas transparency even though the polyimide finally obtained is excellentin heat resistance or dimensional stability. A transmittance withrespect to an electromagnetic wave of at least one wavelength selectedfrom the group consisting of 436 nm, 405 nm, 365 nm, 248 nm and 193 nmis 20% or more, preferably 30%, more preferably 50% or more,particularly preferably 70% or more, when a film having a thickness of 1μm is formed using the polymer precursor. In the polymer precursor ofthe present invention, each transmittance with respect to anelectromagnetic wave of all wavelength including 436 nm, 405 nm and 365nm is preferably 20% or more, more preferably 30% or more, furtherpreferably 50% or more, particularly preferably 70% or more, when a filmhaving a thickness of 1 μm is formed using the polymer precursor.

The effect of high transparency of the polyimide precursor of thepresent invention is more apparent when the film is thick. It is furtherpreferable that a transmittance of the polymer precursor of the presentinvention is 20% or more, preferably 30% or more, more preferably 50% ormore, with respect to an electromagnetic wave of at least one wavelengthselected from the group consisting of 436 nm, 405 nm, 365 nm, 248 nm and193 nm, desirably with respect to an electromagnetic wave of allwavelength of 436 nm, 405 nm and 365 nm, when a film having a thicknessof 2 μm or more, specifically 3 μm, 5 μm or 10 μm, using the polymerprecursor is formed.

Each of 436 nm, 405 nm and 365 nm is an emitting wavelength of ahigh-pressure mercury lamp, generally utilized for exposure of aphotosensitive resin. Each of 248 nm and 193 nm is an emittingwavelength of a laser such as KrF, ArF or the like. High transmittancewith respect to such a wavelength means that loss of light is small anda photosensitive resin composition having high sensitivity can beobtained.

Also, the polyimide finally obtainable from the high transparencypolyimide precursor of the present invention has a high transparency. Itis preferable that a light transmittance of each wavelength in awavelength range between 400 nm and 800 nm is 85% or more when formedinto a film having a thickness of 1 μm, preferably 2 μm. In the casethat the polyimide obtainable as an end product is used for a film orthe like requiring transparency in a visible light range, it is furtherpreferable that a total light transmittance (JIS K7105) is 90% or more.

The weight average molecular weight of the polyimide precursor of thepresent invention is preferably, depending of the use, in the range of3,000 to 1,000,000, more preferably 5,000 to 500,000, further preferably10,000 to 500,000. If the weight average molecular weight is 3,000 orless, sufficient strength cannot be obtained when a coating layer or afilm is made. Also, the strength of the film decreases when a heatingtreatment or the like is performed to obtain polyimide. If the weightaverage molecular weight is 10,000 or less, number of ends of polymers,which cause coloring, relatively increases, thereby coloring may becaused in polyimide to be obtained. On the other hand, if the weightaverage molecular weight exceeds 1,000,000, a viscosity increases andsolubility declines, hence, it is hard to obtain a coating layer or afilm having a smooth surface and a uniform thickness.

The molecular weight used herein means a polystyrene calibrated value bythe gel permeation chromatography (GPC). The value may be of a molecularweight of the polyimide precursor itself or after a chemical imidizationtreatment by acetic anhydride or the like.

The polyimide precursor of the present invention has excellent storagestability since a reverse reaction is hard to proceed. Specifically,preferable storage stability is a rate of change of 20% or less,preferably 10% or less, more preferably 5% or less, in terms of thepolystyrene calibrated-weight average molecular weight by the gelpermeation chromatography of a 0.5 wt % solution of the polyimideprecursor in N-methylpyrrolidone solvent substantially containing waterafter stored at 23° C. for 25 hours. Further, it is also preferable thatrates of change is 20% or less, preferably 10% or less, more preferably5% or less, in terms of the polystyrene calibrated-weight averagemolecular weight by the gel permeation chromatography of the 0.5 wt %solution after stored at 23° C. for 50 hours, 150 hours and 300 hours.Herein, “substantially containing water” means, as mentioned above,N-methylpyrrolidone is in a state without dehydration and a state inwhich a percentage of water content in N-methylpyrrolidone is 0.001 wt %to 10 wt %, further 0.005 wt % to 1 wt %.

The polyimide obtainable from the polyimide precursor of the presentinvention also keeps original properties of polyimide such as heatresistance, dimensional stability, insulation and the like, which areexcellent. For example, a 5% reduction in weight temperature measured innitrogen atmosphere of the polyimide obtainable from the polyimideprecursor of the present invention is preferably 250° C. or more, morepreferably 300° C. or more. Particularly, in the case that its use is anelectronic part or the like, the production method of which includes asolder reflow process, if the 5% reduction in weight temperature is 300°C. or less, there is a risk that a defect such as a bubble or the likemay occur due to a cracked gas generated in the solder reflow process.Herein, the 5% reduction in weight temperature means a temperature atwhich a weight of a sample is reduced by 5% of an initial weight (thatis to say, a temperature at which the weight of the sample is reduced to95% of the initial weight) when a weight decrement is measured by meansof the thermogravimetric analyzer. Similarly, a 10% reduction in weighttemperature means a temperature at which a weight of a sample is reducedby 10% of an initial weight.

Higher glass transition temperature of the polyimide obtainable from thepolyimide precursor of the present invention is better from theviewpoint of heat resistance, however, if a use may include athermoforming process such as an optical waveguide, a glass transitiontemperature is preferably about 120° C. to 380° C., more preferablyabout 200° C. to 380° C. Herein, the glass transition temperature in thepresent invention can be obtained from a peak temperature of tan δ (tanδ=loss elastic modulus (E″)/storage elastic modulus (E′)) by a dynamicviscoelasticity measurement. The dynamic viscoelasticity measurement canbe conducted by, for example, a viscoelasticity analyzer (product name:Solid Analyzer RSA II, manufactured by Rheometric Scientific Inc.) at afrequency of 3 Hz and a heating rate of 5° C./min.

From the viewpoint of dimensional stability of polyimide obtainable fromthe polyimide precursor of the present invention, the coefficient oflinear thermal expansion is preferably 70 ppm or less, more preferably60 ppm or less, further preferably 40 ppm or less. In the case of usingthe polyimide precursor of the present invention for a semiconductorelement or the like to form on a silicon wafer, the coefficient oflinear thermal expansion is preferably 20 ppm or less from the viewpointof adhesion property and warp of a substrate. Herein, the coefficient oflinear thermal expansion in the present invention is a value measured bymeans of a thermo mechanical analysis device (for example, product name:Thermo Plus TMA8310, manufactured by Rigaku Corporation) under thecondition of a heating rate of 10° C./min and a tensile load of 1g/25,000 μm² so that a load per area of cross section of an evaluatingsample is equal.

As aforementioned, the polyimide obtainable from the polyimide precursorof the present invention exhibits excellent transparency withoutintroducing fluorine or an alicyclic structure. Hence, conventionallyunavoidable problems due to the introduction of the fluorine or thealicyclic structure such as lowering of original physical properties offinally obtainable polyimide such as heat resistance, dimensionalstability or the like, and rise of cost can be solved. Also, a coatinglayer, film or molded article of the polyimide having heat resistanceequal to conventional aromatic polyimide can be obtained.

The polyamic acid, which is a precursor, of the present invention may besubject to a coating or molding process for producing a product ormember as it is. Further, a polyimide precursor resin composition may beprepared by dissolving or dispersing the polyamic acid in a solvent ifrequired and compounding a photo- or heat-curable component, anon-polymerizable binder resin other than the polyimide precursor of thepresent invention and other components.

As a solvent to dissolve, disperse or dilute the polyimide precursorresin composition, various general solvents may be used. Also, in thecase of using the polyamic acid, which is a precursor, a solutionobtained by a synthesizing reaction of polyamic acid may be used as itis and other components may be mixed therein, if necessary.

As a usable general solvent, for example, there may be ethers such asdiethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether,ethylene glycol diethyl ether, propylene glycol dimethyl ether,propylene glycol diethyl ether or the like; glycol monoethers (that is,so called cellosolves) such as ethylene glycol monomethyl ether,ethylene glycol monoethyl ether, propylene glycol monomethyl ether,propylene glycol monoethyl ether, diethylene glycol monomethyl ether,diethylene glycol monoethyl ether or the like; ketones such as methylethyl ketone, acetone, methyl isobutyl ketone, cyclopentanone,cyclohexanone or the like; esters such as ethyl acetate, butyl acetate,n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate,acetic ester of the above-mentioned glycol monoethers (for example,methyl cellosolve acetate, ethyl cellosolve acetate), methoxypropylacetate, ethoxypropyl acetate, dimethyl oxalate, methyl lactate, ethyllactate or the like; alcohols such as ethanol, propanol, butanol,hexanol, cyclohexanol, ethylene glycol, diethylene glycol, glycerin orthe like; halogenated hydrocarbons such as methylene chloride,1,1-dichloroethane, 1,2-dichloroethylene, 1-chloropropane,1-chlorobutane, 1-chloropentane, chlorobenzene, bromobenzene,o-dichlorobenzene, m-dichlorobenzene or the like; amides such asN,N-dimethylformamide, N,N-dimethylacetamide or the like; pyrrolidonessuch as N-methyl pyrrolidone or the like; lactones such asγ-butyrolactone or the like; sulfoxides such as dimethyl sulfoxide orthe like, other organic polar solvents or the like. Moreover, there maybe aromatic hydrocarbons such as benzene, toluene, xylene or the likeand other organic nonpolar solvents or the like. These solvents can beused alone or in combination.

As a photocurable component, a compound having one or more ethylenicallyunsaturated bonds may be used. For example, there may be aromatic vinylcompounds such as an amide-based monomer, a (meth)acrylate monomer, anurethane (meth)acrylate oligomer, a polyester (meth)acrylate oligomer,epoxy (meth)acrylate, and (meth)acrylate containing a hydroxyl group,styrene or the like. Also, if the polyimide precursor has a carboxylicacid component such as polyamic acid or the like in its structure, acontrast of dissolving rate of an exposed portion and an unexposedportion becomes larger when and a photosensitive resin composition ismade using an ethylenically unsaturated bond containing compound havinga tertiary amino group in comparison with the case not using the samesince an ionic bond is formed with carboxylic acid of the polyimideprecursor. Herein, “(meth)acrylate” means either acrylate ormethacrylate.

When using such a photocurable compound having an ethylenic unsaturatedbond, a photoradical generator may be further added. As the photoradicalinitiator, there may be, for example, benzoin and alkyl ether thereofsuch as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoinisopropyl ether or the like; acetophenone such as acetophenone,2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone,1,1-dichloroacetophenone, 1-hydroxyacetophenone,1-hydroxycyclohexylphenyl ketone,2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propane-1-one or thelike; anthraquinone such as 2-methylanthraquinone, 2-ethylanthraquinone,2-tertial-butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinoneor the like; thioxanthone such as 2,4-dimethylthioxanthone,2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone or the like; ketal such as acetophenonedimethylketal,benzyldimethylketal or the like; monoacylphosphineoxide orbisacylphosphineoxide such as2,4,6-trimethylbenzoyldiphenylphosphineoxide or the like; benzophenonessuch as benzophenone or the like; xanthones or the like.

Also, even if tertiary amine such as N-phenyldiethanolamine,triethanolamine, triethylamine, N,N-diethylaminobenzene,diazabicyclooctane or the like is added to the polyimide precursor ofthe present invention, a charge transfer complex is formed with thepolyimide precursor by absorption of ultraviolet ray, thus, solubilityto a developer can be changed (K. K. NTS, Latest polyimide, P. 340-341,2002).

Besides the above, photosensitivity may be imparted to the polyimideprecursor itself by introducing a photosensitive portion to thepolyimide precursor of the present invention.

Or, a resin composition may be prepared by adding a photosensitivecomponent which generates acid or base by absorption of anelectromagnetic wave or a photosensitive component which exhibits othereffect by absorption of an electromagnetic wave, and introducing anindirect photosensitive portion which reacts by the effect of thesephotosensitive components to the polyimide precursor of the presentinvention.

As the compound generating acid by light, there may be a photosensitivediazoquinone compound having a 1,2-benzoquinonediazide or1,2-naphthoquinonediazide structure, which is proposed in U.S. Pat. No.2,772,972, U.S. Pat. No. 2,797,213 and U.S. Pat. No. 3,669,658. Forexample, there may be a phenol compound having naphthoquinonediazidesulfonate bonded as ester, an amino compound havingnaphthoquinonediazide sulfonate bonded as amide or the like. As thenaphthoquinonediazide sulfonate, there may be1,2-naphthoquinone-2-diazide-5-sulfonate and1,2-naphthoquinone-2-diazide-4-sulfonate.

Specifically, for example, the following can be exemplified.

wherein, at least one of “R” is “Q” and the rest of “R” is a hydrogenatom.

The compounding amount in the case of using such a photosensitivediazoquinone compound is preferably 0.5 to 50 parts by weight, morepreferably 1 to 40 parts by weight with respect to 100 parts by weightof the polyimide precursor.

If the compounding amount is below 0.5 parts by weight, an excellentpattern cannot be obtained. If the compounding amount exceeds 40 partsby weight, physical properties of a layer of an obtained pattern or thatwith a heating treatment may decrease. Specifically, layer strength,heat resistance and flexibility are often declined. Further, decrease inlayer thickness after a heating treatment becomes apparent.

Also, a conventional photoacid generator such as triazine and aderivative thereof, a sulfonate oxime ester compound, an iodoniumsulfonate salt, a sulfonium sulfonate salt or the like can be used.

As a compound which generates base by light, there may be, for example,2,6-dimethyl-3,5-dicyano-4-(2′-nitrophenyl)-1,4-dihydropyridine,2,6-dimethyl-3,5-diacetyl-4-(2′-nitrophenyl)-1,4-dihydropyridine,2,6-dimethyl-3,5-diacetyl-4-(2′,4′-dinitrophenyl)-1,4-dihydropyridine orthe like. When they are exposed to an active ray, a molecular structurechanges through an intramolecular rearrangement to a structure having apyridine skeleton so as to exhibits basicity. Then, after a heatingtreatment at 150° C. or more, imidization of the polyimide precursorproceeds and solubility decreases, thus, an excellent negative typepattern can be formed.

In order to impart a process property or various functionalities to theresin composition of the present invention, various organic or inorganiclow molecules or polymer compounds may be also compounded besides theabove. For example, dyes, surfactants, leveling agents, plasticizers,microparticles, sensitization agents or the like maybe used. Themicroparticles may include organic microparticles such as polystyrene,polytetrafluoroethylene or the like, inorganic microparticles such ascolloidal silica, carbon, phyllosilicate or the like, which may beporous or have a hollow structure. Examples of the function or form ofthese microparticles include pigments, fillers, fibers or the like.

The polyimide precursor resin composition of the present inventiongenerally contains the polyimide precursor represented by the formula(1a) and/or (1b) in the range of 5 to 99.9 wt % with respect to thetotal amount of solids of the resin composition. Also, a compoundingratio of other optional components is preferably in the range of 0.1 wt% to 95 wt % with respect to the total amount of solids of the polyimideprecursor resin composition. If the proportion is less than 0.1 wt %, itis difficult to exhibit the effect of the added additives whereas if theproportion exceeds 95% by weight, it is difficult to reflect thecharacteristics of the resin composition upon an end product. It is tobe noted that the solid content of the polyimide precursor resincomposition means the whole components other than solvents, and a liquidmonomer component is included in the solid content.

The polyimide precursor resin composition of the present invention maybe used in all known fields and products such as pattern-formingmaterials (resists), coating materials, paints, printing inks,adhesives, fillers, semiconductor elements, electronic materials,optical circuit parts, molding materials, resist materials, buildingmaterials, three-dimensional articles, optical members or the like.

Particularly, the polyimide precursor resin composition of the presentinvention has high sensitivity as absorption wavelength becomes shorterwavelength and can apply an electromagnetic wave having shorterwavelength which is conventionally not able to use besides originalproperties of polyimide to be finally obtained such as heat resistance,dimensional stability, insulation or the like, hence, a finer patterncan be formed.

As aforementioned, the polymer precursor of the present inventionexhibits high transmittance in a shorter wavelength range with respectto an electromagnetic wave since absorption in a long wavelength rangevanishes or becomes smaller by disconnecting or weakening a conjugatedstate, which is likely to be formed in the molecule of the precursorsince the polymer precursor of the present invention has a part whichsequences an unsaturated bond having a π electron orbit and a singlebond alternately, due to a three-dimensional structure of the molecule.

Therefore, the polymer precursor of the present invention having aphotosensitive portion introduced or a resin composition prepared byusing the polymer precursor and a photosensitive component can be usedas a photosensitive resin material which has high sensitivity andcapable of exposure with an electromagnetic wave of a shorterwavelength.

According to the above methods, superior transparency can be obtainedwithout declining useful properties in which the polymer compound, whichis an end product, originally has in comparison with the case that alight absorption wavelength range becomes shorter wavelength byintroducing other chemical structure or a substituent in the molecule.

Also, the high transparency polyimide precursor of the present inventionexhibits excellent transparency without introducing fluorine or analicyclic structure. Hence, the high transparency polyimide precursor ofthe present invention having the photosensitive portion introduced or aresin composition prepared by using the polymer precursor and thephotosensitive component can be used as a photosensitive polyimideprecursor or a photosensitive polyimide precursor resin compositionwhich has high sensitivity.

Due to such a mechanism, transparency can be maintained with any kindsof diamine to react, and conventionally unavoidable problems due to theintroduction of the fluorine or the alicyclic structure such as loweringof original physical properties of polyimide such as heat resistance,dimensional stability or the like, and rise of cost can be solved. Also,a coating layer, film or molded article of the polyimide having heatresistance equal to conventional aromatic polyimide can be obtained.

Also, the resin composition containing the polyimide precursor of thepresent invention has high sensitivity. The polyimide obtainabletherefrom has heat resistance, dimensional stability and insulation,thus, it is suitable as a film or a coating layer for all member towhich polyimide is applied conventionally. For example, the polyimide isexpected to be utilized for semiconductor elements, optical circuitparts, electronic parts, display members for color filters or the likeas a film, a structure or a coating layer having high heat resistance.

The present invention may not be limited to the above embodiments. Theabove embodiments are merely examples, and any one having substantiallythe same constitution and effect as the technical idea disclosed in thescope of the claims of the present invention is included in thetechnical scope of the present invention.

EXAMPLES Production Example 1

A 2 L eggplant-shape flask was charged with 15 g (74 mmol) of pyrene andthe pyrene was dissolved by dichloromethane of 320 ml. After the pyrenewas completely dissolved, 320 ml of acetonitrile and 480 ml of distilledwater were added and agitated. Thereto, 150 g of sodium periodate as anoxidant and 650 mg of ruthenium (III) chloride as a catalyst were addedand agitated at ambient temperature for 22 hours. After reaction, aprecipitate was filtrated, and the precipitate was extracted usingacetone and filtrated. After the extracted acetone was condensed anddried, reflux was performed using dichloromethane for four hoursfollowed by filtrating to obtain a powder. Until the powder wascompletely changed to a white color, the extraction using acetone andreflux using dichloromethane were repeated, thereby 10.2 g of2,2′,6,6′-biphenyltetracarboxylic acid was obtained.

The obtained 2,2′,6,6′-biphenyltetracarboxylic acid was refluxed usingacetic anhydride for three hours, and then the solvent was removed. Theobtained solid substance was refined by sublimation under the conditionof a pressure of 0.8 mmHg (106.4 Pa) and a temperature of 230° C.,thereby a desired white powder of 2,2′,6,6′-biphenyltetracarboxylicdianhydride (2,2′,6,6′-BPDA) was obtained.

Example 1

A 50 ml three-neck flask was charged with 1.20 g (6 mmol) of4,4′-diaminodiphenyl ether and the 4,4′-diaminodiphenyl ether wasdissolved by 5 ml of N-methyl-2-pyrrolidone (NMP) dehydrated, thenagitated under nitrogen flow while cooling the flask in an ice bath.Thereto, 1.77 g (6 mmol) of 2,2′,6,6′-BPDA divided into 10 equal partswas added little by little every 30 minutes. After addition, thesolution was agitated in an ice bath for 5 hours. The solvent wasre-precipitated by dehydrated diethyl ether. The precipitate was driedfor 17 hours at ambient temperature under reduced pressure. Thereby,2.81 g of a white solid substance (Precursor 1) was obtained.

Example 2

A 50 ml eggplant-shape flask was charged with 400 mg of the precursorsynthesized in Example 1 and 4 ml of NMP dehydrated and agitated.Thereto, 2 ml of acetic anhydride was added and agitated at 100° C. for24 hours. The solution was re-precipitated using diethyl ether. Thereby,370 mg of a white powder was obtained (Polyimide 1).

The weight average molecular weight with polystyrene standard using GPC(gel-permeation chromatography) was 64,000.

Example 3

A 50 ml eggplant-shape flask was charged with 400 mg of the precursorsynthesized in Example 1 and 4 ml of NMP dehydrated, and agitated.Thereto, 2 ml of trifluoroacetic anhydride was added and agitated at100° C. for 24 hours. The solution was re-precipitated using diethylether. Thereby, 370 mg of a white powder (Polyimide 2) was obtained. Theweight average molecular weight with polystyrene standard using GPC was13,000.

Example 4

400 mg of the precursor synthesized in Example 1 was dissolved in NMPdehydrated to be 15 wt o, spin coated directly on a glass, and dried ona hot plate heated to 140° C. for 30 minutes. Then, by heating at 300°C. for 1 hour in an oven under the air, polyimide (Polyimide 3)insoluble to NMP was obtained.

Example 6

A 50 ml three-neck flask was charged with 1.20 g (6 mmol) of4,4′-diaminodiphenyl ether. The 4,4′-diaminodiphenyl ether was dissolvedby 5 ml of N-methyl-2-pyrrolidone (NMP), and agitated under nitrogenflow at ambient temperature. Thereto, 1.77 g (6 mmol) of 2,2′,6,6′-BPDAwas added at a time. By addition, a large heat generation was observed.After addition, the solution was agitated for 5 hours andre-precipitated by diethyl ether dehydrated. Thereby, 2.12 g of a lightbrown powder (Precursor 2) was obtained.

Example 7

A 50 ml eggplant-shape flask was charged with 400 mg of the precursorsynthesized in Example 1 and 4 ml of NMP dehydrated, and agitated.Thereto, 2 ml of acetic anhydride was added and agitated at 100° C. for24 hours. The solution was re-precipitated using diethyl ether. Thereby,350 mg of a light brown powder (Polyimide 4) was obtained. The weightaverage molecular weight with polystyrene standard using GPC was 6,800.

Example 8

A 100 ml three-neck flask was charged with 1.08 g (10 mmol) ofparaphenylene diamine and the paraphenylene diamine was dissolved by22.1 ml of N-methyl-2-pyrrolidone (NMP) dehydrated, then agitated undernitrogen flow while cooling the flask in an ice bath. Thereto, 2.94 g(10 mmol) of 2,2′,6,6′-BPDA divided into 10 equal parts was added littleby little every 30 minutes. After addition, the solution was agitated inan ice bath for 1 hour. The solvent was re-precipitated by dropping to 2L of dehydrated diethyl ether. The precipitate was dried for 17 hours atambient temperature under reduced pressure. Thereby, 2.91 g of a whitesolid substance (Precursor 3) was obtained.

Example 9

A 100 ml three-neck flask was charged with 2.92 g (10 mmol) of 1,4-bis(4-aminophenoxy)benzene and the 1,4-bis (4-anaminphenoxy)benzene wasdissolved by 32.2 ml of N-methyl-2-pyrrolidone (NMP) dehydrated, thenagitated under nitrogen flow while cooling the flask in an ice bath.Thereto, 2.94 g (10 mmol) of 2,2′,6,6′-BPDA divided into 10 equal partswas added little by little every 30 minutes. After addition, thesolution was agitated in an ice bath for 1 hour. The solvent wasre-precipitated by dropping to 2 L of dehydrated diethyl ether. Theprecipitate was dried for 17 hours at ambient temperature under reducedpressure. Thereby, 5.78 g of a white solid substance (Precursor 4) wasobtained.

Example 10

A 100 ml three-neck flask was charged with 2.92 g (10 mmol) of1,3-bis(4-aminophenoxy)benzene and the 1,3-bis(4-aminophenoxy)benzenewas dissolved by 32.2 ml of N-methyl-2-pyrrolidone (NMP) dehydrated,then agitated under nitrogen flow while cooling the flask in an icebath. Thereto, 2.94 g (10 mmol) of 2,2′,6,6′-BPDA divided into 10 equalparts was added little by little every 30 minutes. After addition, 5 mlof dehydrated NMP was added and the solution was agitated in an ice bathfor 1 hour. The solvent was re-precipitated by dropping to 2 L ofdehydrated diethyl ether. The precipitate was dried for 17 hours atambient temperature under reduced pressure. Thereby, 5.61g of a whitesolid substance (Precursor 5) was obtained.

Comparative Synthesis Example 1

A 100 ml three-neck flask was charged with 2.00 g (10 mmol) ofdiaminodiphenyl ether and the diaminodiphenyl ether was dissolved by23.8 ml of N-methyl-2-pyrrolidone (NMP) dehydrated, then agitated undernitrogen flow while cooling the flask in an ice bath. Thereto, 2.18 g(10 mmol) of pyromellitic dianhydride divided into 10 equal parts wasadded little by little every 30 minutes. After addition, the solutionwas agitated in an ice bath for 1 hour. The solvent was re-precipitatedby dropping to 2 L of dehydrated acetone. The precipitate was dried for17 hours at ambient temperature under reduced pressure. Thereby, 3.99 gof a white solid substance (Comparative precursor 1) was obtained.

Comparative Synthesis Example 2

A 100 ml three-neck flask was charged with 2.00 g (10 mmol) ofdiaminodiphenyl ether and the diaminodiphenyl ether was dissolved by28.0 ml of N-methyl-2-pyrrolidone (NMP) dehydrated, then agitated undernitrogen flow while cooling the flask in an ice bath. Thereto, 2.94 g(10 mmol) of 3,3′,4,4′-BPDA divided into 10 equal parts was added littleby little every 30 minutes. After addition, the solution was agitated inan ice bath for 1 hour. The solvent was re-precipitated by dropping to 2L of acetone. The precipitate was dried for 17 hours at ambienttemperature under reduced pressure. Thereby, 4.69 g of a white solidsubstance (Comparative precursor 2) was obtained.

[Structure of Polyimide Precursor]

Using DMSO-d₃ as a solvent, two-dimensional spectra of ¹H-NMR, ¹³C-NMRand C—H of the Precursor 1 were measured by means of JN MLA400WBmanufactured by JEOL Ltd. As a result, it was anticipated from signalsof protons of aromatic series derived from2,2′,6,6′-BPDA that there werefollowing two isomers, namely a trans isomer having amide bonds ondifferent aromatic rings and a cis isomer having amide bonds on the samearomatic ring.

That is, it can be considered that the reaction of 2,2′,6,6′-BPDA anddiamine proceeds stepwise. When an amino group of diamine reacts withone acid anhydride group of 2,2′,6,6′-BPDA, reactivity of two carbonylgroups of the other acid anhydride group changes whether the diamine iselectron donating or electron attracting. If the amide bond produced bythe reaction with the diamine is more electron attracting thancarboxylic acid, electrophilicity of carbon of the carbonyl group whichforms an acid anhydride group on the same aromatic ring as the amidegroup increases. As a result, the reactivity with the diamine increasesso as to be the cis isomer. To the contrary, if carboxylic acid is moreelectron attracting than the amide bond produced, electrophilicity ofcarbon of the carbonyl group which forms an acid anhydride group on thesame aromatic ring as the carboxylic acid increases. As a result, thereactivity of the diamine increases so as to be the trans isomer.Therefore, it seems that cis-trans can be controlled by adjusting anelectronic state of the diamine.

[Evaluation of Transparency 1]

The 15 wt % NMP solvent of the Precursor 1 was spin coated on a glass toform a coating layer. A transmittance of the coating layer was measuredby means of a spectrometer (product name: UV-2550 (PC) S GLP,manufactured by Shimadzu Corporation). The solvent of the Precursor 1was spin coated, dried at 140° C. on a hot plate, thus obtained thecoating layer of 15.9 μm.

As a result, as shown in FIG. 2, the transmittance was excellent such as99% at 436 nm, 98% at 405 nm and 91% at 365 nm.

[Evaluation of Transparency 2]

Each of 20 wt % NMP solvents of the Precursors 1, 3, 4 and 5 and theComparative precursors 1 and 2 was spin coated on a glass and heated ona hot plate at 100° C. for 10 minutes. Thereby, a coating layer having amean thickness of 3.5 μm was obtained. The transmittance of the coatinglayer was measured by means of a spectrometer (product name: UV-2550(PC) S GLP, manufactured by Shimadzu Corporation).

As a result, as shown in FIG. 4 and Table 1, the Precursors 1, 3, 4 and5 exhibited excellent transmittance. To the contrary, the Comparativeprecursors 1 and 2 were particularly low in transmittance in lowwavelength range.

TABLE 1 Transmittance [%] 436 nm 405 nm 365 nm Precursor 1 98.7 97.988.3 Precursor 3 97.3 95.6 64.1 Precursor 4 98.8 98.1 91.9 Precursor 598.1 97.0 88.1 Comparative 97.3 81.9 9.7 precursor 1 Comparative 98.092.4 25.5 precursor 2

Table 1 shows the results of measuring a layer having a thickness of 3.5μm. Each transmittance of layers having a thickness of 1 μm and 10 μmwas calculated using the results based on the Lambert-Beer Law as shownbelow. The calculated results are shown in Tables 2 and 3 respectively.

Specifically, according to the Lambert-Beer Law, a transmittance T is asfollows:

Log₁₀(1/T)=kcb

wherein, k=substance-specific constant number; c=concentration; andb=optical path.

In the case of a transmittance of a film, provided that density isconstant even if a layer thickness changes, “c” is also a constantnumber. Thus, the above formula can be represented by the followingformula using a constant number “f”:

Log₁₀(1/T)=fb

wherein, f=kc.

Herein, if a transmittance of a layer having a certain thickness isknown, a substance-specific constant number “f” of each substance can becalculated. For example, the transmittance of the Precursor 3 is 64.1%at 365 nm when a layer thickness is 3.5 μm, thus, Log₁₀(1/0.641)=f×3.5.The substance-specific constant number “f” of the precursor 3 at 365 nmcan be calculated as 0.00552.

Hence, if a target layer thickness is assigned to “b” in the formula ofT=1/10^(0.00552·b), for example, in the case that the target layerthickness is 1 μm, if 1 is assigned to “b”, the transmittance of thePrecursor 3 at 365 nm when the target layer thickness is 1 μm can becalculated as T=0.882.

TABLE 2 Transmittance when layer thickness is 1 μm (calculated value)Transmittance [%] 436 nm 405 nm 365 nm Precursor 1 99.6 99.4 96.5Precursor 3 99.2 98.7 88.1 Precursor 4 99.7 99.5 97.6 Precursor 5 99.599.1 96.4 Comparative 99.2 94.5 51.3 precursor 1 Comparative 99.4 97.867.6 precursor 2

TABLE 3 Transmittance when layer thickness is 10 μm (calculated value)Transmittance [%] 436 nm 405 nm 365 nm Precursor 1 96.3 94.1 70.1Precursor 3 92.5 87.9 28.1 Precursor 4 96.6 94.7 78.6 Precursor 5 94.791.7 69.6 Comparative 92.5 56.5 0.1 precursor 1 Comparative 94.4 79.82.0 precursor 2

[Evaluation of Storage Stability]

The change in molecular weight of a prepared 0.5 wt % NMP solution ofeach Precursor 1, 3, 4 and 5 when stored at 23° C. was measured. In theexperiment, only the Precursor 1 used a sample synthesized under thecondition that the amounts of starting material and the solvent, usedequipments and the like are doubled in scale than those disclosed inExample 1. The results of molecular weight change are showing in Table4.

The NMP used for preparing the solvent is a normal one and notdehydrated.

The measurement conditions are as follows:

-   Equipment: HLC-8120 GPC system, manufactured by Tosoh Corporation;-   Column: TSK gels α−M×2;-   Solvents: NMP dissolving lithium bromide and phosphoric acid    respectively by the concentration of 0.03 mol/L;-   Temperature: 40° C.; and-   Flow rate: 500 μl/min.

TABLE 4 Change in weight average molecular weight of the polyimideprecursor of the present invention 0 hr 25 hrs 50 hrs 150 hrs 300 hrsPrecursor 1 42000 41000 42100 42100 41000 Precursor 3 27900 28900 2890029200 27500 Precursor 4 43700 43400 44900 44500 44000 Precursor 5 8190076800 78700 78000 81500

In the similar manner, the change in molecular weight of each of theComparative precursors 1 and 2 was measured. However, the column of GPC(the gel permeation chromatography) used for measuring the molecularweight was clogged and the measurement was unable to conduct. Accordingto the document disclosed in the past (J. A. Kreuz, J. Polym. Sci.; PartA; Polym. Chem. 1990 28 3787), the weight average molecular weight of acompound corresponding to the Comparative compound 1 is initially106,000 and becomes 69,000 after 25 hours under nearly the samecondition. Also, the weight average molecular weight of a compoundcorresponding to the Comparative compound 2 is initially 90,100 and isreduced to 61,200.

From the above results, the polyimide precursor of the present inventionexhibits stable weight average molecular weight during storage. It canbe understood that the structure of the polyimide precursor of thepresent invention is effective against decrease in molecular weightduring storage at room temperature, which is a problem of a normalpolyamic acid.

[Evaluation of Thermophysical Properties 1]

An NMP solvent of the Polyimide 1 was coated on a film (product name:UPILEX S 50S, manufactured by Ube Industries, Ltd.) attached on a glass.After drying at 140° C. on a hot plate for 30 minutes, peeling wasperformed, thus obtained a film having a thickness of 5 μm. Similarly, a15 wt % NMP solvent of the Precursor 1 was coated on a film (productname: UPILEX S 50S, manufactured by Ube Industries, Ltd.) attached on aglass. After drying at 140° C. on a hot plate for 30 minutes followed bypeeling, the peeled film was heated at 300° C. in an oven in the air for1 hour, thus obtained a polyimide film having a thickness of 45 μm(Polyimide 3).

(Evaluation of Dynamic Viscoelasticity)

A dynamic viscoelasticity measurement of each film was conducted bymeans of a viscoelasticity analyzer (product name: Solid Analyzer RSAII, manufactured by Rheometric Scientific Inc.) at a frequency of 3 Hzand a heating rate of 5° C./min.

As a result, as shown in FIGS. 3A and 3B, since each of the films has apeak of tan δ at around 350° C., the Tg (glass transition temperature)of each polyimide is 350° C. Also, since the Polyimide 1 is in a rubberyregion (a region wherein E′ and E″ are constant) at a temperature highertan Tg in view of behavior of storage elastic modulus (E′) and losselastic modulus (E″) at a temperature higher than Tg, the observationsuggests that the Polyimide 1 is a crosslinked product. Since E′ and E″keeps on decreasing at a temperature higher than Tg, the observationsuggests that the Polyimide 3 is not a crosslinked product. Thereby, thepolyimide formed by the polyimide precursor of the present invention isexcellent in heat resistance.

(Evaluation of Coefficient of Linear Thermal Expansion)

Each of the above film was cut into width of 5 mm×length of 20 mm to beused as an evaluation sample. A coefficient of linear thermal expansionwas measured by means of a thermo mechanical analysis device (productname: Thermo Plus TMA8310, manufactured by Rigaku Corporation). Themeasurement condition of the evaluation samples was an observed lengthof 15 mm, a heating rate of 10° C./min, and a tensile load of 1 g/25000μm² so that a load per area of cross section of the evaluation sample isequal. The coefficient of linear thermal expansion of the Polyimide 1was measured with a tensile load of 1 g and the coefficient of linearthermal expansion of the Polyimide 3 was measured with a tensile load of5 g.

As a result, the coefficient of linear thermal expansion at 50° C. to100° C. of the Polyimide 1 was 27 ppm and that of the Polyimide 3 was 25ppm. A flexion point of expansion of the film of each polyimide was 315°C.

[Evaluation of Thermophysical Properties 2]

The 20 wt % NMP solvent of each of the Precursors 3, 4 and 5 was spincoated on a glass. After drying at 100° C. for 10 minutes, thetemperature was raised from room temperature to 300° C. at a rate of 10°C./min. in nitrogen atmosphere. Then, 300° C. was maintained for 1 hour,thus obtained Polyimide films 3a, 4a and 5a (thickness of 10±1.5 μm).

The dynamic viscoelasticity evaluation and the coefficient of linearthermal expansion evaluation of each film were performed under thesimilar condition as above (tensile load was 2 g). Tg and thecoefficient of linear thermal expansion were measured. The results areshown in Table 5.

TABLE 5 Thermophysical properties of polyimide film of the presentinvention Coefficient of linear Tg thermal expansion Polyimide film3a >400° C.  25.5 Polyimide film 4a 345° C. 50.6 Polyimide film 5a 315°C. 61.6

Example 11

A photosensitive resin composition (Photosensitive resin composition 1)was prepared by adding and dissolving the Precursor 5 and the followingphotosensitive substance by 20 wt % with respect to the Precursor 5 inNMP so that a solid content is 20 wt %:

[Evaluation of Photosensitivity]

The Photosensitive resin composition 1 was spin coated on chrominium ofa chrominium plated glass, and dried on a hot plate at 100° C. for 10minutes. In this way, two kinds of coating layer respectively having athickness of 1.25 μm and 2.8 μm were obtained.

Each of the coating layers was exposed by means of a manual exposureequipment (MA-1200, manufactured by Dainippon Screen Mfg. Co., Ltd.).Only 365 nm light was taken from light from a high-pressure mercury lampusing an i-ray pass filter and used for the exposure.

The exposure was conducted by various exposures. After each coatinglayer was dipped in a 0.1 wt % TMAH aquesous solution for 30 secondswhile slowly being stirred by means of a magnetic stirrer, each coatinglayer was dipped in distilled water for 10 seconds to rinse off. Arelationship between a standardized layer thickness after drying andexposures was plotted to obtain sensitivity.

As a result, the sensitivity was significantly excellent, wherein theremaining layer was 0 at 120 mJ/cm² when a layer thickness was 2.8 μmand at 110 mJ/cm² when a layer thickness was 1.25 μm as shown in FIG. 5.These results were obtained because the photosensitive substance wasable to utilize light from the light source efficiently since thetransmittance of the precursor was excellent.

[Pattern Forming]

Furthermore, the Photosensitive resin composition 1 was used to form apattern.

In the same manner as the evaluation of the photosensitivity, after acoating layer having a thickness of 2 μm was formed followed byirradiation with an electromagnetic wave only of 150 mJ/cm² and 365 nmvia a photomask, the coating layer was dipped in a 0.1 wt % TMAHaquesous solution for 30 seconds while slowly being stirred by means ofa magnetic stirrer. Then, the coating layer was dipped in distilledwater for 10 seconds to rinse off followed by drying.

The layer sample was heated in an oven at 300° C. in nitrogen atmospherefor 1 hour. A pattern was confirmed by means of a microscope.

As a result, as shown in FIG. 6, the pattern was resolved to 8 μm/8 μmline and space. The layer thickness after baking was 1.1 μm.

Also, a coating layer of the Photosensitive resin composition 1 coatedon a glass in the same manner as above was heated at 300° C. in nitrogenatmosphere for 1 hour. The coating layer was dipped in distilled waterfor 24 hours and peeled from the glass, thus a film having a thicknessof 10 μm was obtained. As the result of the dynamic viscoelasticityevaluation and the thermo mechanical analysis, Tg was 350° C. and acoefficient of linear thermal expansion was 63.9 ppm.

In comparison with the data of the Precursor 5 before exposure, thecoefficient of linear thermal expansion was larger by just under 2 ppm,however, Tg increased. It is presumed that this is due to the effectthat the Photosensitive substance 1 becomes a high reactive substancesuch as carbene or the like when decomposes by heat and becomes acrosslinked portion of a polymer chain or the like.

According to these results, as the polyimide formed by the polyimideprecursor of the present invention has excellent heat resistance andcapable of producing a film having a low coefficient of expansion, thepolyimide is suitable for forming products of fields in which thesecharacteristics are advantageous, for example, paints, printing inks,color filters, flexible displays, electronic parts, layer insulationfilms, wire cover films, optical circuits, optical circuit parts,antireflection films, holograms, other optical members or buildingmaterials.

Also, since the polyimide precursor of the present invention isexcellent in storage stability and transmittability of anelectromagnetic wave, a photosensitive resin composition high insensitivity and excellent in storage stability can be obtained when thepolyimide precursor of the present invention is applied to thephotosensitive resin composition.

1. A polyimide precursor resin composition containing a hightransparency polyimide precursor consisting of repeating unitsrepresented by the following formula (3), wherein a rate of change interm of the polystyrene calibrated-weight average molecular weight bygel permeation chromatography of a 0.5 wt % solution of the polyimideprecursor in N-methylpyrrolidone solvent substantially containing wateris 20% or less after stored at 23° C. for 25 hours:

wherein each of R¹ to R⁶ is independently a hydrogen atom or amonovalent organic group, which may be bonded to each other; each of R⁷,R⁸, R¹¹ and R¹² is independently a hydrogen atom, a halogen atom, ahydroxyl group, a mercapto group, a cyano group, a silyl group, asilanol group, an alkoxy group, a nitro group, a carboxyl group, anacetyl group, an acetoxy group, a sulfo group, a saturated orunsaturated alkyl group, a saturated or unsaturated halogenated alkylgroup, an aromatic group, an allyl group or an ethylenically unsaturatedbond-containing group; X is a divalent organic group having an aromaticring; each of R⁹, R¹⁰, R¹³ and R¹⁴ is independently a hydrogen atom or amonovalent organic group; Y is a tetravalent organic group; Z is adivalent organic group having an aromatic ring; groups represented bythe same symbol among repeating units in the same molecule may bedifferent atoms or structures; and o, p and q are natural numbers of 0or more in the condition that at least one of o, p and q is a naturalnumber of 1 or more, and further wherein a total amount of the repeatingunits (1a) and (1b) in the formula (3) is 50% by mole or more ofrepeating units constituting a polymer skeleton of the high transparencypolyimide precursor.
 2. A polyimide precursor resin compositionaccording to claim 1, wherein the high transparency polyimide precursorhas a photosensitive portion which cures the polyimide precursor resincomposition or changes solubility of the polyimide precursor resincomposition when irradiated with radiation having a wavelength of 440 nmor less in a molecule; and/or the polyimide precursor resin compositionfurther contains a photosensitive component having the photosensitiveportion.
 3. A polyimide precursor resin composition according to claim1, further comprising a photosensitive diazoquinone compound.
 4. Apolyimide precursor resin composition according to claim 1, wherein thepolyimide precursor resin composition is used as a pattern formingmaterial.
 5. A polyimide precursor resin composition according to claim1, wherein the polyimide precursor resin composition is used as a paintor a printing ink; or a forming material of color filters, flexibledisplay films, electronic parts, layer insulation films, wire coverfilms, optical circuits, optical circuit parts, antireflection films,holograms, optical members or building materials.